Device and method for detecting complex surface topography of a curved microlens array

Abstract

The curved micro-lens array complex surface appearance detection device and method can realize high-precision, high-resolution and high-efficiency curved micro-lens array surface appearance detection, and can detect and analyze the surface appearances of the curved base and the micro-lens unit part of the curved micro-lens array respectively, and has high flexibility. The curved micro-lens array complex surface appearance detection device comprises a monochromatic laser light source (1), a beam expander lens group (2), a beam splitter (3), a phase shift device (4), a plane reference mirror (5), a compensation lens (6), a curved micro-lens array sample (7), an imaging lens (8), a plane array detector (9) and a computer processing system (10).

Description

Technical Field

[0001] This invention relates to the technical field of precision optical testing, and more particularly to a device for detecting the complex surface morphology of a curved microlens array, and the method used in this device. Background Technology

[0002] Microlens arrays are optical elements that have the characteristics of lenses arranged periodically in an array on their surface structure. The size of their lens units is mostly from a few micrometers to hundreds of millimeters, which is much smaller than that of conventional lenses, hence the name microlens.

[0003] In recent years, with the deepening research on microlens arrays, curved microlens arrays, as a branch of microlens arrays, have developed rapidly. Traditional microlens arrays are mainly planar microlens arrays, where the microlens units are distributed on a planar substrate, and the base height and optical axis direction of each unit are consistent. In contrast, the microlens units of curved microlens arrays are distributed on a curved substrate, and the base height and optical axis direction of each unit are not consistent. Curved microlens arrays are mainly used in imaging systems to obtain a larger field of view and better image quality. Patents such as CN201410806265.0 and CN202011132753.X describe this technology.

[0004] To improve the fabrication level and work quality of curved microlens arrays, surface morphology inspection is crucial. Surface morphology inspection of such components falls under the field of micro / nanostructure morphology inspection. Existing micro / nanostructure morphology inspection technologies mainly include atomic force microscopy, scanning electron microscopy, confocal microscopy, and white light interferometry. These technologies can achieve relatively high inspection accuracy and resolution. However, the first three require point-by-point scanning, which is inefficient. White light interferometry is suitable for large-area array inspection, but for components like curved microlens arrays with large axial sag spans, it requires long-term, large-area axial scanning, also failing to achieve efficient inspection.

[0005] Phase-shifting interferometry is also an important method for detecting the morphology of micro and nano structures. It uses monochromatic light illumination and has the same high-precision, high-resolution area array detection capability, and does not require axial scanning. However, the current phase-shifting interferometry can only detect micro and nano structures on planar substrates and cannot effectively detect features on curved substrates. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a device for detecting the complex surface morphology of curved microlens arrays. This device can achieve high-precision, high-resolution, and high-efficiency detection of the surface morphology of curved microlens arrays, and can detect and analyze the surface morphology of the curved substrate and the microlens unit part of the curved microlens array separately, thus possessing high flexibility.

[0007] The technical solution of the present invention is: This curved microlens array complex surface morphology detection device includes: a monochromatic laser source (1), a beam expander lens group (2), a beam splitter (3), a phase shifter (4), a plane reference mirror (5), a compensation lens (6), a curved microlens array sample (7), an imaging lens (8), an area array detector (9), and a computer processing system (10).

[0008] A monochromatic laser source emits a narrow laser beam, which is then expanded into a wide parallel laser beam by a beam expander lens group. This wide parallel laser beam is incident on a beam splitter, splitting into a reflected beam and a transmitted beam. The reflected beam strikes a plane reference mirror, is reflected back along its original path, passes through the beam splitter again, is transmitted through the beam splitter, and then passes through an imaging lens to reach the area array detector, forming a reference beam. The transmitted beam continues to propagate forward, passes through a compensation lens, is converged, and then projected onto the surface of a curved microlens array sample. After being reflected by the sample, it passes through the compensation lens, is reflected again by the beam splitter, and then passes through the imaging lens to reach the area array detector, forming a measurement beam. The measurement beam and the reference beam interfere with each other, forming an interference pattern. The plane reference mirror is mounted on a phase-shifting device, which controls the precise axial movement of the plane reference mirror, repeating the above interference process to generate a phase-shifted interferogram. This phase-shifted interferogram is acquired by the area array detector and then transmitted to a computer processing system for analysis and computation.

[0009] The monochromatic laser source of this invention emits a thin laser beam, which is then expanded into a wide parallel laser beam by a beam expander lens group. This wide parallel laser beam is incident on a beam splitter and split into two beams: a reflected beam and a transmitted beam. The reflected beam illuminates a planar reference mirror, is reflected back along its original path, passes through the beam splitter again, is transmitted through the beam splitter, and then passes through an imaging lens to reach the area array detector, forming a reference beam. The transmitted beam continues to propagate forward, passes through a compensation lens, is converged, and then projected onto the surface of a curved microlens array sample. After being reflected by the sample, it passes through the compensation lens, is reflected again by the beam splitter, passes through the imaging lens, and reaches the area array detector, forming a measurement beam. The measurement beam and the reference beam interfere with each other. The planar reference mirror is mounted on... In the phase-shifting device, the planar reference mirror is precisely moved axially by controlling the phase-shifting device, and the above interference process is repeated to generate a phase-shifted interferogram. The phase-shifted interferogram is acquired by the area array detector and then transmitted to the computer processing system for analysis and calculation. This invention is based on the phase-shifting interferometry method. According to the characteristic that the surface of the curved microlens array can be divided into a curved substrate and microlens units, a curved wavefront matching the curved substrate is generated by a compensation lens. The surface morphology of the curved substrate and the microlens units is detected by zero-compensation interference and partial-compensation interference, respectively. Therefore, it can achieve high-precision, high-resolution, and high-efficiency surface morphology detection of curved microlens arrays. Moreover, it can detect and analyze the surface morphology of the curved substrate and the microlens units of the curved microlens array separately, and has high flexibility.

[0010] A method for detecting the complex surface morphology of curved microlens arrays is also provided, which includes the following steps:

[0011] (1) The initial phase is calculated based on the phase-shifted interferogram. The initial phase distribution W is obtained by solving the phase and phase junction of the phase-shifted interferogram collected by the array detector and transmitted to the computer processing system.

[0012] (2) Divide the area of ​​the curved substrate and the microlens unit, and record the initial phase within the area of ​​the curved substrate as W. Base The initial phase within the range of the microlens unit is recorded as Where i is the serial number of the microlens unit;

[0013] (3) Calculate the surface topography error of the curved substrate. Within the range of the curved substrate defined in step (2), calculate the surface topography error S of the curved substrate according to the following formula. Base for:

[0014] S Base =W Base / twenty one);

[0015] (4) Calculate the surface topography error of the microlens unit. Within the range of the microlens units defined in step (2), calculate the surface topography error of the microlens unit according to the following formula. for:

[0016]

[0017] Among them, R i To compensate for the theoretical value of the sag of the wavefront projected onto the microlens unit from the lens exit, α is the theoretical value of the sagittal height of the microlens unit. i To compensate for the angle between the wavefront emitted from the lens and the normal of the microlens unit, i is the serial number of the microlens unit.

[0018] (5) Calculate the complete surface morphology of the curved microlens array sample, based on the surface morphology error S of the curved substrate in step (3). Base Surface topography error of the microlens unit in step (4) And to compensate for the exit wavefront R of the lens, calculate the complete surface morphology S of the curved microlens array sample. Fin for:

[0019]

[0020] Among them, the wavefront R emitted by the compensation lens is taken as the theoretical value or the actual value is taken after detection by an actual wavefront detection device. Attached Figure Description

[0021] Figure 1 This is a flowchart of the method described in this invention.

[0022] Figure 2 This is a structural diagram of the device described in a specific embodiment of the present invention.

[0023] Figure 3 This is a phase-shifting interferogram from an embodiment of the present invention.

[0024] Figure 4 This refers to the initial phase distribution in the embodiments described in this invention.

[0025] Figure 5 This refers to the initial phase within the curved base area in the embodiments of the present invention.

[0026] Figure 6 This refers to the initial phase within the microlens unit range described in the embodiments of the present invention.

[0027] Figure 7 This refers to the surface topography error of the curved substrate in the embodiments of the present invention.

[0028] Figure 8This refers to the surface topography error of the microlens unit in the embodiments of the present invention.

[0029] Figure 9 This is the complete surface morphology of the curved microlens array sample in the embodiments of the present invention. Detailed Implementation

[0030] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0031] It should be noted that the term "comprising" and any variations thereof in the specification, claims and accompanying drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, apparatus, product or device that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products or devices.

[0032] like Figure 2 As shown, this device for detecting complex surface morphology of curved microlens array includes: a monochromatic laser source 1, a beam expander lens group 2, a beam splitter 3, a phase shifter 4, a plane reference mirror 5, a compensation lens 6, a curved microlens array sample 7, an imaging lens 8, a surface array detector 9, and a computer processing system 10.

[0033] A monochromatic laser source emits a narrow laser beam, which is then expanded into a wide parallel laser beam by a beam expander lens group. This wide parallel laser beam is incident on a beam splitter, splitting into a reflected beam and a transmitted beam. The reflected beam strikes a plane reference mirror, is reflected back along its original path, passes through the beam splitter again, is transmitted through the beam splitter, and then passes through an imaging lens to reach the area array detector, forming a reference beam. The transmitted beam continues to propagate forward, passes through a compensation lens, is converged, and then projected onto the surface of a curved microlens array sample. After being reflected by the sample, it passes through the compensation lens, is reflected again by the beam splitter, and then passes through the imaging lens to reach the area array detector, forming a measurement beam. The measurement beam and the reference beam interfere with each other, forming an interference pattern. The plane reference mirror is mounted on a phase-shifting device, which controls the precise axial movement of the plane reference mirror, repeating the above interference process to generate a phase-shifted interferogram. This phase-shifted interferogram is acquired by the area array detector and then transmitted to a computer processing system for analysis and computation.

[0034] The monochromatic laser source of this invention emits a thin laser beam, which is then expanded into a wide parallel laser beam by a beam expander lens group. This wide parallel laser beam is incident on a beam splitter and split into two beams: a reflected beam and a transmitted beam. The reflected beam illuminates a planar reference mirror, is reflected back along its original path, passes through the beam splitter again, is transmitted through the beam splitter, and then passes through an imaging lens to reach the area array detector, forming a reference beam. The transmitted beam continues to propagate forward, passes through a compensation lens, is converged, and then projected onto the surface of a curved microlens array sample. After being reflected by the sample, it passes through the compensation lens, is reflected again by the beam splitter, passes through the imaging lens, and reaches the area array detector, forming a measurement beam. The measurement beam and the reference beam interfere with each other. The planar reference mirror is mounted on... In the phase-shifting device, the planar reference mirror is precisely moved axially by controlling the phase-shifting device, and the above interference process is repeated to generate a phase-shifted interferogram. The phase-shifted interferogram is acquired by the area array detector and then transmitted to the computer processing system for analysis and calculation. This invention is based on the phase-shifting interferometry method. According to the characteristic that the surface of the curved microlens array can be divided into a curved substrate and microlens units, a curved wavefront matching the curved substrate is generated by a compensation lens. The surface morphology of the curved substrate and the microlens units is detected by zero-compensation interference and partial-compensation interference, respectively. Therefore, it can achieve high-precision, high-resolution, and high-efficiency surface morphology detection of curved microlens arrays. Moreover, it can detect and analyze the surface morphology of the curved substrate and the microlens units of the curved microlens array separately, and has high flexibility.

[0035] Preferably, the operating wavelength of the monochromatic laser light source is determined based on the surface reflectivity of the curved microlens array sample.

[0036] Preferably, the working spectral range of the beam expander lens group is selected according to the wavelength of the monochromatic laser source.

[0037] Preferably, the compensation lens is used to generate a curved wavefront that matches the F-number of the curved substrate of the curved microlens array sample. Matching the F-number means that the F-number of the compensation lens should be greater than or equal to the F-number of the curved substrate.

[0038] Preferably, the center of the curved substrate of the curved microlens array sample coincides with the focal point of the compensation lens.

[0039] Preferably, the area array detector is located at the image plane of the imaging lens.

[0040] Preferably, during the measurement process, the laser emits a laser with a center wavelength of 632.8 nm; the working wavelength of the beam expander lens group matches the laser emission wavelength, and the beam diameter after expansion is 50.8 mm; the planar reference mirror is mounted on the phase shifting device; the diameter of the compensation lens is 50.8 mm, and the F-number of the compensation lens is 4; the center position of the curved substrate of the curved microlens array sample coincides with the focal position of the compensation lens, the radius of curvature of the curved substrate is 50 mm, the F-number of the curved substrate is 1, and the F-number of the compensation lens is 4, which is greater than or equal to the F-number of the curved substrate and meets the requirements; the magnification of the imaging lens is 4 times; and the area array detector is placed at the image plane position of the imaging lens.

[0041] like Figure 1 As shown, a method for detecting the complex surface morphology of a curved microlens array is also provided, which includes the following steps:

[0042] (1) The initial phase is calculated based on the phase-shifted interferogram. The initial phase distribution W is obtained by solving the phase and phase junction of the phase-shifted interferogram collected by the array detector and transmitted to the computer processing system.

[0043] (2) Divide the area of ​​the curved substrate and the microlens unit, and record the initial phase within the area of ​​the curved substrate as W. Base The initial phase within the range of the microlens unit is recorded as Where i is the serial number of the microlens unit;

[0044] (3) Calculate the surface topography error of the curved substrate. Within the range of the curved substrate defined in step (2), calculate the surface topography error S of the curved substrate according to the following formula. Base for:

[0045] S Base =W Base / twenty one);

[0046] (4) Calculate the surface topography error of the microlens unit. Within the range of the microlens units defined in step (2), calculate the surface topography error of the microlens unit according to the following formula. for:

[0047]

[0048] Among them, R i To compensate for the theoretical value of the sag of the wavefront projected onto the microlens unit from the lens exit, α is the theoretical value of the sagittal height of the microlens unit. i To compensate for the angle between the wavefront emitted from the lens and the normal of the microlens unit, i is the serial number of the microlens unit.

[0049] (5) Calculate the complete surface morphology of the curved microlens array sample, based on the surface morphology error S of the curved substrate in step (3).Base Surface topography error of the microlens unit in step (4) And to compensate for the exit wavefront R of the lens, calculate the complete surface morphology S of the curved microlens array sample. Fin for:

[0050]

[0051] Among them, the wavefront R emitted by the compensation lens is taken as the theoretical value or the actual value is taken after detection by an actual wavefront detection device.

[0052] The following details specific embodiments of the present invention.

[0053] A surface morphology detection device for curved microlens arrays based on partially compensated interference, such as Figure 2 As shown, it includes a monochromatic laser source 1, a beam expander lens group 2, a beam splitter 3, a phase shifter 4, a plane reference mirror 5, a compensation lens 6, a curved microlens array sample 7, an imaging lens 8, a surface array detector 9, and a computer processing system 10.

[0054] The target element in this embodiment is a reflective curved microlens array made of aluminum. Both the curved substrate and the microlens units are spherical. The surface morphology is detected using the method proposed in this invention. During the measurement process, laser 1 emits a laser with a center wavelength of 632.8 nm; the working wavelength of the beam expander lens group 2 matches the output wavelength of laser 1, and the beam diameter after expansion is 50.8 mm; the planar reference mirror 5 is mounted on the phase shifting device 4; the diameter of the compensation lens 6 is 50.8 mm, and the F-number of the compensation lens 6 is 4; the center position of the curved substrate of the curved microlens array sample 7 coincides with the focal position of the compensation lens 6, the radius of curvature of the curved substrate is 50 mm, the F-number of the curved substrate is 1, and the F-number of the compensation lens 6 is 4, which is greater than or equal to the F-number of the curved substrate, meeting the requirements of this invention; the magnification of the imaging lens 8 is 4 times; and the area array detector 9 is placed at the image plane position of the imaging lens 8.

[0055] The surface morphology detection method for curved microlens arrays based on partially compensated interference according to the present invention is performed according to the following steps.

[0056] Based on step one, the initial phase is calculated using the phase-shifting interferogram. The phase-shifting interferogram acquired by the area array detector 9 and transmitted to the computer processing system 10 is shown below. Figure 3 As shown, the initial phase distribution W is obtained after unwinding and phase concatenation. The initial phase distribution W is as follows: Figure 4 As shown.

[0057] Based on step two, the boundaries of the curved substrate and the microlens unit are defined, and the initial phase within the curved substrate is recorded as W. Base ,like Figure 5As shown; the initial phase within the range of the microlens unit is recorded as like Figure 6 As shown, i is the serial number of the microlens unit, and the total number of microlens units is...

[0058] Based on step three, calculate the surface topography error S of the curved substrate. Base ,like Figure 7 As shown.

[0059] According to step four, calculate the surface morphology error of the microlens unit. Where i is the serial number of the microlens unit, and the surface topography error of the microlens unit is... like Figure 8 As shown.

[0060] Based on step five, calculate the complete surface morphology of the curved microlens array sample 10, and based on the surface morphology error S of the curved substrate in step three. Base Surface topography error of the microlens unit in step four And by compensating for the wavefront R of the exit lens 6, the complete surface morphology S of the curved microlens array sample 10 is obtained. Fin like Figure 9 As shown, the outgoing wavefront R of the compensation lens 6 is taken as the theoretical value.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for detecting complex surface morphology of curved microlens arrays, characterized in that: It includes the following steps: (1) The initial phase is calculated based on the phase-shifted interferogram. The initial phase distribution is obtained by dephase and phase unwrapping based on the phase-shifted interferogram acquired by the area array detector and transmitted to the computer processing system. ; (2) Divide the area of ​​the curved substrate and the microlens unit, and record the initial phase within the area of ​​the curved substrate. The initial phase within the range of the microlens unit is recorded as ,in This is the serial number of the microlens unit; (3) Calculate the surface topography error of the curved substrate. Within the range of the curved substrate defined in step (2), calculate the surface topography error of the curved substrate according to the following formula. for: （1）； (4) Calculate the surface morphology error of the microlens unit. Within the range of the microlens unit divided in step (2), calculate the surface morphology error of the microlens unit according to the following formula. for: （2） in, To compensate for the theoretical value of the sag of the wavefront projected onto the microlens unit from the lens exit, This is the theoretical value of the sagittal height of the microlens unit. To compensate for the angle between the wavefront exiting the lens and the normal of the microlens unit, This is the serial number of the microlens unit; (5) Calculate the complete surface morphology of the curved microlens array sample, based on the surface morphology error of the curved substrate in step (3). Surface topography error of the microlens unit in step (4) and the wavefront of the compensation lens. Calculate the complete surface morphology of the curved microlens array sample. for: （3） Among them, the wavefront of the compensation lens Take the theoretical value or the actual value after detection using an actual wavefront detection device.

Images