Test system and test method for deflection angle of micro-mirror in MEMS micro-mirror array

Abstract

This invention discloses a testing system and method for measuring the deflection angle of micromirrors in a MEMS micromirror array. The testing method includes: providing a collimated light beam that passes through a beam splitter with an effective aperture smaller than the beam aperture; reflecting the collimated beam through the beam splitter to a two-dimensional scanning mirror, and then focusing it onto a target micromirror in the MEMS micromirror array located at the focal plane by a focusing lens; the target micromirror reflecting the beam back along the original optical path, deflecting it again by the beam splitter to a detection module to obtain light intensity information; calculating the deflection angle of the micromirror based on a pre-established light intensity-angle correspondence; controlling the two-dimensional scanning mirror to sequentially focus the beam onto the remaining micromirrors, repeating the above steps until all tests are completed. The testing system and method for measuring the deflection angle of micromirrors in a MEMS micromirror array of this invention can perform independent, rapid, and non-contact measurement of the deflection angle of each micromirror in a MEMS micromirror array, and is particularly suitable for micrometer-scale, high-density integrated MEMS micromirror arrays.

Description

Technical Field

[0001] This invention belongs to the field of MEMS micromirror array detection technology, specifically relating to a testing system and method for testing the deflection angle of micromirrors in a MEMS micromirror array. Background Technology

[0002] MEMS micromirror arrays are a type of miniature mirror array device fabricated using semiconductor microfabrication processes, enabling precise control of light beam direction. Depending on the size of the micromirrors, MEMS micromirror arrays are typically categorized into different scales, such as micrometer-scale, hundred-micrometer-scale, and even millimeter-scale. For hundred-micrometer-scale or millimeter-scale MEMS micromirror arrays, typical applications are concentrated in optical information exchange systems, such as optical switches. For micrometer-scale micromirror arrays, the most typical application is currently in projection display systems, where each micromirror can independently modulate the transmission time or luminous flux of incident light, thereby forming an image with grayscale information, such as a Digital Micromirror Device (DMD).

[0003] The core function of MEMS micromirrors lies in achieving precise control of beam direction; therefore, accurate acquisition and control of their deflection angle is crucial. Existing measurement methods include capacitance-based detection methods and diffraction pattern-based detection methods. Capacitance-based detection methods require integrating capacitor structures and detection circuits around the micromirrors. However, for small, densely packed micron-scale micromirror arrays, it is difficult to integrate additional structures within a limited space, thus limiting their application in large-scale arrays. Diffraction pattern-based detection methods mainly reflect the overall diffraction characteristics of the array. When only some micromirrors in the array are deflected, the impact on the overall diffraction pattern is small, making it difficult to achieve independent evaluation of individual micromirrors.

[0004] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a testing system and method for the deflection angle of micromirrors in a MEMS micromirror array. This system can independently, quickly, and non-contactly measure the deflection angle of each micromirror in the MEMS micromirror array, and is especially suitable for micron-scale, high-density integrated MEMS micromirror arrays.

[0006] To achieve the above objectives, a specific embodiment of the present invention provides the following technical solution: a method for testing the deflection angle of micromirrors in a MEMS micromirror array, comprising the following steps:

[0007] Provide a collimated beam to pass through a beam splitter, wherein the effective aperture of the beam splitter is smaller than the aperture of the collimated beam;

[0008] The collimated beam passing through the beam splitter is incident on the two-dimensional scanning mirror mechanism, and the collimated beam reflected by the two-dimensional scanning mirror is focused onto a target micromirror in the MEMS micromirror array by the focusing lens, wherein the MEMS micromirror array is located at the focal plane of the focusing lens;

[0009] The target micromirror reflects the focused beam back along the original optical path. The returned beam is collimated again after passing through the focusing lens and is reflected again by the two-dimensional scanning mirror to the beam splitter. The beam splitter deflects the returned beam to the detection module.

[0010] The detection module obtains the light intensity information of the reflected light from the target micromirror;

[0011] Based on the pre-established correspondence between light intensity information and micromirror deflection angle, the deflection angle of the micromirror is calculated.

[0012] The two-dimensional scanning mirror mechanism is controlled to focus the collimated beam sequentially onto all other target micromirrors in the MEMS micromirror array. The steps of acquiring light intensity information and calculating deflection angle are repeated for each target micromirror until the deflection angle test of all target micromirrors in the MEMS micromirror array is completed.

[0013] In one or more embodiments of the present invention, the step of controlling the two-dimensional scanning mirror mechanism to sequentially focus the collimated beam onto all other target micromirrors in the MEMS micromirror array includes:

[0014] The two-dimensional scanning mirror mechanism is controlled to scan the incident light beam from one side to the other side in the first row of the MEMS micromirror array, so that the incident light beam after passing through the focusing lens is sequentially focused on each micromirror in the row.

[0015] After completing the scan of the current row, the two-dimensional scanning mirror mechanism is controlled to deflect the incident beam longitudinally by a preset angle so as to move to the position of the adjacent next row of micromirrors.

[0016] The two-dimensional scanning mirror mechanism is controlled to make the incident beam scan back to the side in the next row in the horizontal direction, so that the incident beam is focused on each micromirror in the row in sequence.

[0017] Repeat the above longitudinal deflection and lateral reciprocating scanning steps until all micromirrors in the MEMS micromirror array are covered.

[0018] In one or more embodiments of the present invention, the step of obtaining the pre-established correspondence between light intensity information and micromirror deflection angle includes:

[0019] The control and testing system measures the undeflected standard micromirror to obtain initial light intensity information;

[0020] The standard micromirror is controlled to be deflected to multiple different preset angles in sequence, and the corresponding deflection light intensity information is measured using the test system at each preset angle.

[0021] Based on the initial light intensity information and the deflection light intensity information corresponding to each preset angle, a calibration curve between light intensity information and deflection angle is fitted and established.

[0022] The calibration curve represents the pre-established correspondence between light intensity information and micromirror deflection angle.

[0023] In one or more embodiments of the present invention, the effective aperture of the beam splitter is less than or equal to 70% of the aperture of the incident beam; and / or, the reflectivity of the beam splitter is 70% to 90%.

[0024] A specific embodiment of the present invention also provides a testing system for the deflection angle of micromirrors in a MEMS micromirror array, including a light source, a collimating lens, a beam splitter, a two-dimensional scanning mirror mechanism, a focusing lens, and a detection module. The collimating lens is used to convert the light emitted by the light source into a collimated incident beam. The beam splitter is disposed downstream of the collimating lens group, and the effective aperture of the beam splitter is smaller than the aperture of the incident beam. The two-dimensional scanning mirror mechanism is used to reflect the incident beam passing through the beam splitter onto the MEMS micromirror array to be tested. The focusing lens is located between the two-dimensional scanning mirror mechanism and the MEMS micromirror array to be tested, and is used to focus the incident beam reflected by the two-dimensional scanning mirror mechanism onto the MEMS micromirror array to be tested. The detection module detects the light intensity of the reflected beam, which is formed by the incident beam being reflected by the micromirror. After being collimated by the focusing lens, the reflected beam is sequentially reflected by the two-dimensional scanning mirror mechanism to the beam splitter, and then reflected by the beam splitter to the detection module. The two-dimensional scanning mirror mechanism is used to change the direction of the incident beam so that the incident beam after passing through the focusing lens can be sequentially focused onto different micromirrors in the MEMS micromirror array. The testing system can calculate the deflection angle of each micromirror based on the light intensity information of the reflected beam detected by the detection module.

[0025] In one or more embodiments of the present invention, the effective aperture of the beam splitter is less than or equal to 70% of the incident beam aperture; and / or, the reflectivity of the beam splitter is 70% to 90%.

[0026] In one or more embodiments of the present invention, the test system further includes a light-absorbing box located on the beam path of the incident beam reflected by the beam splitter.

[0027] In one or more embodiments of the present invention, the detection module includes a detection lens and a detection mechanism, wherein the detection lens is used to focus the reflected light beam onto the detection mechanism, and the detection mechanism is used to detect the light intensity information of the reflected light beam.

[0028] In one or more embodiments of the present invention, the detection mechanism includes a photodiode, a transimpedance amplifier, an analog-to-digital converter, and a central processing unit; the photodiode is used to convert an optical signal into a current signal; the transimpedance amplifier is connected to the photodiode and is used to convert the current signal into an amplified voltage signal; the analog-to-digital converter is connected to the transimpedance amplifier and is used to convert the voltage signal into a digital voltage signal; the central processing unit is connected to the analog-to-digital converter and is used to receive the digital voltage signal transmitted by the analog-to-digital converter to obtain the digital amplitude of the digital voltage signal, wherein the digital amplitude is the light intensity information.

[0029] In one or more embodiments of the present invention, the aperture of the incident beam focused by the focusing lens is smaller than the aperture of the micromirrors in the MEMS micromirror array.

[0030] Compared with the prior art, the beneficial effects of the testing system and method for measuring the deflection angle of micromirrors in a MEMS micromirror array of the present invention are as follows:

[0031] (1) Independent measurement of individual micromirrors is possible: By introducing a combination of a two-dimensional scanning mirror mechanism and a focusing lens, the collimated beam is focused onto each individual target micromirror in the MEMS micromirror array, and the reflected light returning along the original optical path is received, thereby obtaining the light intensity information of each micromirror and calculating its deflection angle. Compared with detection methods based on diffraction patterns (which can only reflect the overall diffraction characteristics of the array and are difficult to distinguish the deflection state of individual micromirrors), this invention can perform independent, fixed-point measurement of any micromirror in the array, and is especially suitable for micron-scale, high-density integrated MEMS micromirror arrays.

[0032] (2) No need to integrate additional structures inside the MEMS micromirror array: The present invention adopts a pure optical external optical path measurement scheme, which does not require the integration of capacitance sensors and their detection circuits inside the MEMS micromirror array. Compared with the detection method based on capacitance sensing (which is limited by the size of the micromirrors and the density of the array, making it difficult to integrate additional structures in a limited space), the present invention has no special requirements for the structure of the micromirrors themselves, and has a wider range of applications, especially suitable for large-scale micromirror arrays with small size and dense arrangement.

[0033] (3) Self-collimation of the optical path and strong anti-interference capability: The reflected light from the target micromirror strictly returns along the original optical path, passes through the same focusing lens and two-dimensional scanning mirror, and is then deflected by the beam splitter to the detection module. This common optical path design effectively reduces the influence of external factors such as environmental vibration and temperature drift on the measurement results, while avoiding alignment errors introduced by optical path separation, thus ensuring the stability and repeatability of the measurement results.

[0034] (4) High testing efficiency and easy automation: By controlling the two-dimensional scanning mirror mechanism to change the beam direction in sequence, all target micromirrors in the MEMS micromirror array can be quickly traversed without manually moving the sample or readjusting the optical path. Combined with automated light intensity acquisition and angle calculation, batch and rapid testing of the deflection angle of the entire array of micromirrors can be realized, significantly improving testing efficiency.

[0035] (5) The system has a simple structure and low cost: The main test components of this invention are conventional optical elements such as collimating light source, beam splitter, two-dimensional scanning mirror, focusing lens and light intensity detection module. It does not require a complex optical path interference system or a high-precision imaging system. The structure is compact, the implementation cost is low, and it is easy to integrate into the existing test platform. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a flowchart of a method for testing the deflection angle of micromirrors in a MEMS micromirror array according to an embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram of the structure and optical path of a testing system for the deflection angle of a micromirror in a MEMS micromirror array according to an embodiment of the present invention;

[0039] Figure 3 This is a partial structural and optical path diagram of a testing system for the deflection angle of micromirrors in a MEMS micromirror array according to an embodiment of the present invention.

[0040] Figure 4 This is a schematic diagram of a beam splitter in one embodiment of the present invention;

[0041] Figure 5 This is a schematic diagram of the arrangement of micromirrors in a MEMS micromirror array and the scanning process of a two-dimensional scanning mechanism in one embodiment of the present invention;

[0042] Figure 6This is a schematic diagram of the detection mechanism in one embodiment of the present invention. Detailed Implementation

[0043] To enable those skilled in the art to better understand the technical solutions in this disclosure, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this disclosure.

[0044] Currently, the existing methods for testing the deflection angle of MEMS micromirror arrays are mainly: capacitance sensing-based detection methods, laser Doppler interferometry-based methods, and diffraction pattern-based detection methods.

[0045] Among these methods, capacitance-based detection requires integrating a capacitor structure and detection circuit around the micromirrors. For small, densely packed micron-scale micromirror arrays, integrating additional structures within a limited space is difficult, thus limiting their application in large-scale arrays. Detection methods based on diffraction patterns primarily reflect the overall diffraction characteristics of the array. When only some micromirrors in the array are deflected, the impact on the overall diffraction pattern is small, making it difficult to independently evaluate individual micromirrors. Laser Doppler interferometry methods typically employ point-by-point scanning detection. When the micromirror array is large, each micromirror needs to be measured individually, usually manually, resulting in low detection efficiency.

[0046] Therefore, this invention provides a testing system and method for measuring the deflection angle of micromirrors in a MEMS micromirror array. Utilizing the aperture limitation of a beam splitter and the focal plane imaging characteristics of a focusing lens, combined with the pointing control capability of a two-dimensional scanning mirror, the collimated beam is focused onto each individual target micromirror in the array. The reflected light from the micromirror then returns along the original optical path and is deflected by the same beam splitter to the detection module, obtaining light intensity information related to the deflection angle. Finally, based on a pre-established correspondence between light intensity and angle, the deflection angle of each micromirror is calculated, and the entire array is automatically traversed. This invention enables independent, rapid, and non-contact measurement of the deflection angle of individual micromirrors in a high-density MEMS micromirror array without integrating additional sensing structures within the array. It also overcomes the technical problems of diffraction methods' inability to distinguish individual mirrors, the difficulty of integration in capacitance methods, and the low efficiency of laser Doppler methods.

[0047] like Figures 1 to 4 As shown, a method for testing the deflection angle of micromirrors in a MEMS micromirror array according to an embodiment of the present invention includes the following steps:

[0048] S1. Provide a collimated beam so that it passes through a beam splitter, wherein the effective aperture of the beam splitter is smaller than the aperture of the collimated beam;

[0049] S2. The collimated beam passing through the beam splitter is incident on the two-dimensional scanning mirror mechanism, and the collimated beam reflected by the two-dimensional scanning mirror is focused onto a target micromirror in the MEMS micromirror array by the focusing lens, wherein the MEMS micromirror array is located at the focal plane of the focusing lens.

[0050] S3. The target micromirror reflects the focused beam back along the original optical path. The returned beam is re-collimated by the focusing lens and reflected again by the two-dimensional scanning mirror to the beam splitter. The beam splitter deflects the returned beam to the detection module.

[0051] S4. The detection module obtains the light intensity information of the reflected light from the target micromirror;

[0052] S5. Based on the pre-established correspondence between light intensity information and micromirror deflection angle, calculate the deflection angle of the micromirror.

[0053] S6. Control the two-dimensional scanning mirror mechanism to focus the collimated beam onto all other target micromirrors in the MEMS micromirror array in sequence. Repeat the steps of acquiring light intensity information and calculating deflection angle for each target micromirror until the deflection angle test of all target micromirrors in the MEMS micromirror array is completed.

[0054] The core detection mechanism of this invention lies in the fact that the effective aperture of the beam splitter is configured to be smaller than the aperture of the collimated beam, making the beam splitter essentially equivalent to a spatial aperture set in the optical path. After the collimated beam passes through the beam splitter, only the portion of the beam corresponding to the effective aperture of the beam splitter is allowed to pass through.

[0055] like Figure 4 As shown, the beam splitter has a blocking region (indicated by the diagonal lines in the figure). This region neither reflects nor transmits the light beam, forming an opaque light-blocking area. The effective aperture of the beam splitter is the central aperture enclosed by this blocking region, and this effective aperture is smaller than the aperture of the incident collimated beam. Therefore, only the central portion of the beam can pass through the beam splitter for subsequent measurements, while the edge portions of the beam are blocked.

[0056] like Figure 2 As shown, when the target micromirror is in an undeflected state, its returning beam returns precisely along the original optical path. After passing through the beam splitter again, the aperture of the returning beam is basically the same as the aperture of the initial collimated beam after passing through the beam splitter. Therefore, the light intensity received by the detection module is the maximum value (or a fixed reference value). Figure 2 In the MEMS micromirror array, the three horizontal bars represent three micromirrors, and the middle micromirror is not deflected.

[0057] like Figure 3 As shown, when the target micromirror deflects, the direction of its returning beam deviates from the original optical path. When this deviated returning beam re-enters the beam splitter, due to the limited effective aperture of the beam splitter (spatial aperture effect), only a portion of the beam can pass through the beam splitter and be deflected to the detection module; the rest is blocked by the beam splitter. The larger the micromirror deflection angle, the more severe the deviation in the direction of the returning beam, the more light is blocked by the beam splitter, and the lower the light intensity received by the detection module. Figure 3 In a beam splitter, the black portion is the ineffective portion, while the transparent portion is the effective aperture. Figure 3 In the MEMS micromirror array, the three horizontal bars represent three micromirrors, with the middle micromirror being deflected.

[0058] Therefore, a monotonically negative correlation (or other pre-calibrated correspondence) is formed between the light intensity information acquired by the detection module and the deflection angle of the micromirror. By pre-establishing a light intensity-angle calibration curve or function, the precise deflection angle of the micromirror can be deduced from the measured light intensity information.

[0059] A combination of a two-dimensional scanning mirror mechanism and a focusing lens is introduced to focus the collimated light beam onto each individual target micromirror in the MEMS micromirror array, and to receive the reflected light returning along the original optical path. By controlling the direction of the two-dimensional scanning mirror mechanism, the light beam can be automatically and quickly switched to the next target micromirror in the array. The steps of acquiring light intensity information and calculating deflection angle are repeated until the deflection angle of all target micromirrors in the MEMS micromirror array is tested, thereby realizing full-array, automated, and batch angle measurement.

[0060] Among them, the two-dimensional scanning mirror mechanism is a common mechanism in existing technology, such as the GVSK2-EC product (two-dimensional galvanometer system kit, silver film reflector, 230VAC), which is mainly used to change the direction of the collimated beam so that the collimated beam can automatically scan each target micromirror in the MEMS micromirror array in sequence.

[0061] like Figure 2 As shown, in one specific embodiment, the "providing a collimated beam" in step S1 is implemented as follows: a device combining a light source and a collimating lens can be used. Specifically, the light beam emitted by the light source is incident on the collimating lens, and after refraction and collimation by the collimating lens, it exits to form a collimated beam with a very small divergence angle (usually less than 0.5 mrad).

[0062] The specific type of light source is not limited; any point light source capable of generating a beam that meets the system's collimation requirements is applicable. For example, the light source can be a coherent source such as a fiber laser, semiconductor edge-emitting laser (EEL), or vertical-cavity surface-emitting laser (VCSEL), or it can be a superluminescent diode (SLD) or other types of incoherent point light sources. Regardless of the light source chosen, as long as the emitted beam, after passing through the collimating lens, forms a collimated beam that meets the requirements for divergence angle and spot size, the testing function of this invention can be achieved.

[0063] The beam splitter design serves a dual purpose: firstly, it allows the collimated beam passing through the beam splitter to be incident on the two-dimensional scanning mirror and subsequent optical path; secondly, it allows the beam returning from the target micromirror along the original optical path to be reflected by the beam splitter to the detection module, thereby achieving effective collection and detection of the returned beam. If a conventional beam splitter or flat glass were used instead, it would be difficult to simultaneously achieve efficient transmission of the incident beam and directional reflection of the returned beam. Based on these functional requirements, this invention optimizes the key parameters of the beam splitter.

[0064] Specifically, the effective aperture of the beam splitter is configured to be less than or equal to 70% of the incident collimated beam aperture. By setting the effective aperture of the beam splitter to be significantly smaller than the beam aperture, the beam splitter also functions as a spatial aperture, which can significantly improve the sensitivity of angle measurement. When the micromirror undergoes a slight deflection, the directional shift of the returning beam will be immediately blocked by the limited aperture, resulting in a significant change in the detected light intensity. The smaller the effective aperture, the higher the angular resolution, but too small an aperture will reduce the signal strength. If the effective aperture of the beam splitter is too large (e.g., greater than 70% of the incident beam aperture), its spatial aperture effect will be significantly weakened, leading to a decrease in the angular resolution of the system for slight micromirror deflections, while stray light interference increases and the measurement signal-to-noise ratio decreases. Therefore, a beam aperture of 50% to 70% is preferred.

[0065] Specifically, the reflectivity of the beam splitter is preferably set to 70%–90%. Too low a reflectivity will result in a weak light signal entering the detection module, reducing the signal-to-noise ratio; too high a reflectivity will result in insufficient energy of the light beam passing through the beam splitter and incident on the micromirror, affecting the effective detection of the returned light intensity. Controlling the reflectivity within the range of 70%–90% ensures sufficient incident light energy and returned light signal intensity while balancing the system's signal-to-noise ratio and detection sensitivity, achieving optimal overall measurement performance.

[0066] In one specific embodiment, the detection module in step S4 can employ commercially available light intensity detection devices. Its core function is to convert the received incident light signal into a quantifiable electrical signal output and provide a specific numerical value. This value directly reflects the intensity of the reflected light beam received by the detection module, thereby achieving precise measurement of the light intensity reflected by the target micromirror. Exemplarily, the detection module can use devices such as photodiodes, avalanche photodiodes (APDs), photomultiplier tubes (PMTs), or photodetectors, or integrated measurement devices such as optical power meters. These devices all possess advantages such as fast response speed, high sensitivity, and good linearity, meeting the real-time acquisition requirements of the reflected light beam intensity information in this invention.

[0067] The selection of the detection module can be flexibly adjusted according to the actual light signal intensity and measurement accuracy requirements. For scenarios with strong returned light signals, a low-cost photodiode combined with a transimpedance amplifier circuit can be used; for scenarios with weak returned light signals requiring high-sensitivity detection, an avalanche photodiode or photomultiplier tube can be selected. Regardless of the device used, it is essential to ensure that its spectral response range matches the wavelength of the light source, and that its output electrical signal has a good linear relationship with the measured light intensity to guarantee the accuracy of subsequent angle calculations.

[0068] In one specific embodiment, step S5, which involves obtaining the pre-established correspondence between light intensity information and micromirror deflection angle, includes:

[0069] S51. The control and testing system measures the undeflected standard micromirror to obtain initial light intensity information.

[0070] This step is the calibration process for the initial light intensity. The control test system measures the standard micromirror in its undeflected state (i.e., deflection angle of 0°) to obtain the initial light intensity information, denoted as I0. This initial light intensity information serves as the benchmark reference value for subsequent calibration calculations, corresponding to the maximum returned light intensity at zero deflection angle.

[0071] S52. Control the standard micromirror to deflect to multiple different preset angles in sequence, and use the test system to measure the corresponding deflection light intensity information at each preset angle.

[0072] Specifically, the standard micromirror is controlled to deflect sequentially to multiple different preset angles θ1, θ2, ..., θ n (For example, with a step interval of 1° or 0.5°), covering its maximum deflection range (such as ±10° or ±12°), and using a test system to measure the corresponding deflection light intensity information I1, I2, ..., I at each preset angle. n The more preset angles there are, i.e., the larger n is, the closer the calibration curve established by subsequent fitting will be to the true light intensity-angle mapping relationship, thus obtaining higher angle measurement accuracy.

[0073] S53. Based on the initial light intensity information and the deflection light intensity information corresponding to each preset angle, a calibration curve between the light intensity information and the deflection angle is fitted and established.

[0074] For example, based on the initial light intensity information I0 and the deflection light intensity information corresponding to each preset angle, with the deflection angle as the independent variable and the normalized light intensity (I / I0) as the dependent variable, a calibration curve between the light intensity information and the deflection angle is established using an appropriate mathematical fitting method (such as linear fitting, polynomial fitting, or spline interpolation). Typically, the light intensity decreases monotonically with increasing deflection angle, and a quadratic polynomial can be used for fitting.

[0075] S54. The calibration curve is a pre-established correspondence between light intensity information and micromirror deflection angle.

[0076] The calibration curve obtained in step S53 is used as a pre-established correspondence between light intensity information and the micromirror deflection angle. In subsequent actual tests of the micromirror, the measured light intensity information is substituted into this calibration curve or its inverse function to calculate the precise deflection angle of the micromirror.

[0077] In one specific embodiment, such as Figure 5 As shown, step S6, which controls the two-dimensional scanning mirror mechanism to sequentially focus the collimated beam onto all other target micromirrors in the MEMS micromirror array, includes:

[0078] S61. Control the two-dimensional scanning mirror mechanism to scan the incident beam from one side to the other side in the first row of the MEMS micromirror array, so that the incident beam after passing through the focusing lens is sequentially focused on each micromirror in the row.

[0079] This step is an in-row forward scan, which involves controlling the two-dimensional scanning mirror mechanism to scan the incident light beam in a stepwise manner along the lateral direction within the first row of the MEMS micromirror array, from one side (e.g., the leftmost side) to the other side (e.g., the rightmost side). This allows the incident light beam, after passing through the focusing lens, to be sequentially focused onto each micromirror in that row. The step interval is equal to the center-to-center distance between the micromirrors in the lateral direction, ensuring that each micromirror can be accurately focused.

[0080] S62. After completing the scanning of the current row, control the two-dimensional scanning mirror mechanism to deflect the incident beam longitudinally by a preset angle so as to move to the position of the adjacent next row of micromirrors.

[0081] This step is a vertical stepping between rows. After completing the scanning of all micromirrors in the current row (such as the first row), the two-dimensional scanning mirror mechanism is controlled to deflect the incident beam by a preset angle in the vertical direction. This preset angle corresponds to the angle change required for the focused spot to move one micromirror row spacing on the array, thereby moving the focused position of the incident beam to the beginning of the adjacent next row of micromirrors (such as the rightmost side).

[0082] S63. Control the two-dimensional scanning mirror mechanism to make the incident beam scan back to one side in the next row in the horizontal direction, so that the incident beam is focused on each micromirror in the row in sequence.

[0083] This step is an in-row reverse scanning, which involves controlling the two-dimensional scanning mirror mechanism to scan the incident beam in reverse along the horizontal direction within the next row, scanning from one side (the rightmost side) back to the other side (the leftmost side), so that the incident beam is sequentially focused on each micromirror in that row. This "bow-shaped" (serpentine) scanning path reduces the ineffective longitudinal movement time and improves scanning efficiency.

[0084] S64. Repeat the above longitudinal deflection and lateral reciprocating scanning steps until all micromirrors in the MEMS micromirror array are covered.

[0085] This step involves repeated traversal, which means repeating the longitudinal deflection in step S62 and the lateral back-and-forth scanning in step S63 (i.e., alternating between scanning one row forward and scanning the next row backward) until all rows and all micromirrors in the MEMS micromirror array are covered, thus completing the scanning test of the entire array. Figure 5 The center line and arrows represent a schematic diagram of the scanning sequence of the two-dimensional scanning mirror mechanism.

[0086] In step S6, the laser (light source) can be pulsed according to the position of each micromirror in the micromirror array, so that the laser beam (collimated beam) illuminates the designated micromirror at the corresponding moment. That is, by scanning line by line through the two-dimensional scanning mirror mechanism, point-by-point detection of each micromirror in the micromirror array can be achieved. The system software can continuously read the light intensity signal reflected back from each micromirror and compare it with the initial reference value, thereby calculating the mechanical deflection angle of each micromirror, realizing the individual testing of micromirrors in the MEMS micromirror array.

[0087] like Figures 2 to 6As shown, a specific embodiment of the present invention also provides a testing system for the deflection angle of micromirrors in a MEMS micromirror array, including a light source, a collimating lens, a beam splitter, a two-dimensional scanning mirror mechanism, a focusing lens, and a detection module; the collimating lens is used to convert the light emitted by the light source into a collimated incident beam; the beam splitter is disposed downstream of the collimating lens group, and the effective aperture of the beam splitter is smaller than the aperture of the incident beam; the two-dimensional scanning mirror mechanism is used to reflect the incident beam passing through the beam splitter onto the MEMS micromirror array to be tested; the focusing lens is located between the two-dimensional scanning mirror mechanism and the MEMS micromirror array to be tested, and is used to reflect the two-dimensional scanning beam onto the MEMS micromirror array to be tested. The incident light beam reflected by the mirror mechanism is focused onto a micromirror in the MEMS micromirror array. The detection module is used to detect the light intensity information of the reflected light beam. The reflected light beam is formed after the incident light beam is reflected by the micromirror. After being collimated by the focusing lens, the reflected light beam is reflected sequentially by the two-dimensional scanning mirror mechanism to the beam splitter, and then reflected by the beam splitter to the detection module. The two-dimensional scanning mirror mechanism is used to change the direction of the incident light beam so that the incident light beam after the focusing lens can be focused sequentially onto different micromirrors in the MEMS micromirror array. The testing system can calculate the deflection angle of each micromirror based on the light intensity information of the reflected light beam detected by the detection module.

[0088] This testing system can be applied to the aforementioned method for testing the deflection angle of micromirrors in MEMS micromirror arrays. Employing a common-path self-collimation design, it converts the micromirror deflection angle into a quantifiable change in light intensity through the small-aperture spatial aperture effect of the beam splitter. Combined with the automatic traversal scanning of the two-dimensional scanning mirror mechanism, it achieves independent, rapid, and non-contact measurement of the deflection angle of individual micromirrors in a MEMS micromirror array, without requiring the integration of additional structures within the micromirror array. This makes it particularly suitable for large-scale MEMS micromirror arrays with micrometer-level, high-density integration.

[0089] Specifically, in this embodiment, the light source, collimating lens, beam splitter, two-dimensional scanning mirror mechanism, focusing lens, and the light source, collimating lens, and focusing lens in the detection module are all existing optical components, which can be directly purchased from commercially available products. The technical innovation of this invention lies not in the improvement of individual components, but in the combination and configuration of the aforementioned existing components according to a specific optical path structure (the effective aperture of the beam splitter is smaller than the beam aperture, the MEMS micromirror array is located at the focal plane of the focusing lens, and the return beam travels through the original optical path to the detection module), thereby achieving independent measurement of the deflection angle of a single micromirror in the dense array. Refer to the relevant descriptions of the light source, collimating lens, and focusing lens in the aforementioned test method.

[0090] In one specific embodiment, the focal length and numerical aperture of the focusing lens are configured such that the aperture of the incident beam focused by the lens on the focal plane of the MEMS micromirror array is smaller than the aperture of a single micromirror in the MEMS micromirror array. This parameter design ensures that the focused beam falls completely on the reflective surface of a single target micromirror, preventing the beam from simultaneously illuminating adjacent micromirrors or the gap between micromirrors, thereby enabling independent excitation and detection of a single micromirror.

[0091] These parameters are crucial for the independent measurement of a single micromirror in this invention. If the focused spot diameter is larger than the micromirror diameter, the incident beam will simultaneously cover multiple micromirrors, and the returned beam will contain reflected or scattered light from adjacent micromirrors. This results in the light intensity information obtained by the detection mechanism failing to accurately reflect the deflection state of a single target micromirror, thus losing the ability to independently evaluate a single micromirror. Therefore, the focused spot diameter should preferably be 1 / 3 to 2 / 3 of the micromirror diameter, ensuring that the beam falls entirely within the target micromirror's range while also allowing for a certain margin for alignment error.

[0092] In one specific embodiment, the effective aperture of the beam splitter is less than or equal to 70% of the incident beam aperture; the reflectivity of the beam splitter is 70%–90%. The selection criteria and function of the beam splitter can be found in the relevant description of the beam splitter in the aforementioned test method.

[0093] like Figure 2 and Figure 6 As shown, the detection module includes a detection lens and a detection mechanism. The detection lens is used to focus the reflected light beam onto the detection mechanism, and the detection module is used to detect the light intensity information of the reflected light beam.

[0094] Specifically, the detection mechanism includes a photodiode, a transimpedance amplifier, an analog-to-digital converter (ADC), and a central processing unit (CPU). The photodiode converts the optical signal into a current signal. The transimpedance amplifier, connected to the photodiode, converts the current signal into an amplified voltage signal. The ADC, connected to the transimpedance amplifier, converts the voltage signal into a digital voltage signal. The CPU, connected to the ADC, receives the digital voltage signal from the ADC to obtain the digitized amplitude of the digital voltage signal, which is the light intensity information. Through this photoelectric conversion and signal processing chain, the weak light signal reflected back by the micromirror is ultimately converted into a calculable digital quantity, used to subsequently calculate the deflection angle of the micromirror based on a pre-established light intensity-angle calibration relationship.

[0095] In this embodiment, the central processing unit can adopt a commercially available processing chip architecture, such as a field-programmable gate array (FPGA), a digital signal processor (DSP), a microcontroller (MCU), or an embedded processor. These devices all have advantages such as fast data processing speed, flexible interfaces, and ease of integration, and can meet the system's requirements for real-time acquisition and processing of light intensity signals.

[0096] In this embodiment, the photodiode, transimpedance amplifier, analog-to-digital converter, and detection lens are all common, commercially available components. The photodiode can be a PIN or avalanche diode (APD), the transimpedance amplifier can be an integrated low-noise operational amplifier chip, and the analog-to-digital converter can be a 12- to 24-bit successive approximation or Δ-Σ ADC chip, depending on the required accuracy. All of these components represent existing, mature technologies, and those skilled in the art can flexibly select them based on measurement accuracy, response speed, and cost requirements. The detection lens can be a conventional convex lens or achromatic lens, both common optical components available on the market.

[0097] like Figure 2 As shown, the testing system also includes a light-absorbing box, which is located on the beam path of the incident beam reflected by the beam splitter. Specifically, when the collimated beam passes through the beam splitter, the beam splitter divides the incident beam into two parts according to its reflectivity: most of the beam (corresponding to transmitted light) passes through the beam splitter and continues to propagate to the two-dimensional scanning mirror mechanism, while the remaining small portion of the beam (corresponding to reflected light) is reflected by the beam splitter to a side optical path. The light-absorbing box is placed on this reflected optical path to absorb this portion of the collimated incident beam reflected by the beam splitter.

[0098] The main function of the light-absorbing box is to prevent stray light beams reflected by the beam splitter from undergoing secondary reflection or scattering in the experimental environment, thereby interfering with the detection mechanism; it also prevents the reflected beams from illuminating other optical components or operators, improving system safety. The light-absorbing box can be a closed box structure internally coated with a black light-absorbing material (such as black velvet, a black oxide coating, or a carbon nanotube light-absorbing layer), which can effectively absorb the light beam incident upon it and reduce stray light reflection. This light-absorbing box is a conventional optical accessory; those skilled in the art can select appropriate dimensions and light-absorbing materials based on the beam aperture and power.

[0099] It will be apparent to those skilled in the art that this disclosure is not limited to the details of the exemplary embodiments described above, and that this disclosure can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of this disclosure is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this disclosure. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0100] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for testing the deflection angle of a micro-mirror in a MEMS micro-mirror array, characterized in that, Includes the following steps: Provide a collimated beam to pass through a beam splitter, wherein the effective aperture of the beam splitter is smaller than the aperture of the collimated beam; The collimated beam passing through the beam splitter is incident on the two-dimensional scanning mirror mechanism, and the collimated beam reflected by the two-dimensional scanning mirror is focused onto a target micromirror in the MEMS micromirror array by the focusing lens, wherein the MEMS micromirror array is located at the focal plane of the focusing lens; The target micromirror reflects the focused beam back along the original optical path. The returned beam is collimated again after passing through the focusing lens and is reflected again by the two-dimensional scanning mirror to the beam splitter. The beam splitter deflects the returned beam to the detection module. The detection module obtains the light intensity information of the reflected light from the target micromirror; Based on the pre-established correspondence between light intensity information and micromirror deflection angle, the deflection angle of the micromirror is calculated. The two-dimensional scanning mirror mechanism is controlled to focus the collimated beam sequentially onto all other target micromirrors in the MEMS micromirror array. The steps of acquiring light intensity information and calculating deflection angle are repeated for each target micromirror until the deflection angle test of all target micromirrors in the MEMS micromirror array is completed.

2. The method of claim 1, wherein the method is used for testing the deflection angle of a MEMS micro-mirror in a MEMS micro-mirror array. The steps of controlling the two-dimensional scanning mirror mechanism to sequentially focus the collimated beam onto all other target micromirrors in the MEMS micromirror array include: The two-dimensional scanning mirror mechanism is controlled to scan the incident light beam from one side to the other side in the first row of the MEMS micromirror array, so that the incident light beam after passing through the focusing lens is sequentially focused on each micromirror in the row. After completing the scan of the current row, the two-dimensional scanning mirror mechanism is controlled to deflect the incident beam longitudinally by a preset angle so as to move to the position of the adjacent next row of micromirrors. The two-dimensional scanning mirror mechanism is controlled to make the incident beam scan back to the side in the next row in the horizontal direction, so that the incident beam is focused on each micromirror in the row in sequence. Repeat the above longitudinal deflection and lateral reciprocating scanning steps until all micromirrors in the MEMS micromirror array are covered.

3. The method of claim 1, wherein the method is used for testing the deflection angle of a MEMS micro-mirror in a MEMS micro-mirror array. The steps to obtain the pre-established correspondence between light intensity information and micromirror deflection angle include: The control and testing system measures the undeflected standard micromirror to obtain initial light intensity information; The standard micromirror is controlled to be deflected to multiple different preset angles in sequence, and the corresponding deflection light intensity information is measured using the test system at each preset angle. Based on the initial light intensity information and the deflection light intensity information corresponding to each preset angle, a calibration curve between light intensity information and deflection angle is fitted and established. The calibration curve represents the pre-established correspondence between light intensity information and micromirror deflection angle.

4. The method of claim 1, wherein the method is used for testing the deflection angle of a MEMS micro-mirror in a MEMS micro-mirror array. The effective aperture of the beam splitter is less than or equal to 70% of the incident beam aperture; and / or, The reflectivity of the beam splitter is 70% to 90%.

5. A system for testing the deflection angle of a micro-mirror in a MEMS micro-mirror array, characterized in that, include: light source; A collimating lens is used to convert light emitted from a light source into a collimated incident beam. A beam splitter is disposed downstream of the collimating lens group, and the effective aperture of the beam splitter is smaller than the aperture of the incident beam. A two-dimensional scanning mirror mechanism is used to reflect the incident light beam passing through the beam splitter onto the MEMS micromirror array to be tested; A focusing lens, located between the two-dimensional scanning mirror mechanism and the MEMS micromirror array to be tested, is used to focus the incident light beam reflected by the two-dimensional scanning mirror mechanism onto a micromirror of the MEMS micromirror array. The detection module is used to detect the light intensity information of the reflected beam. The reflected beam is formed by the incident beam after being reflected by the micromirror. After being collimated by the focusing lens, the reflected beam is reflected sequentially by the two-dimensional scanning mirror mechanism to the beam splitter, and then reflected by the beam splitter to the detection module. The two-dimensional scanning mirror mechanism is used to change the direction of the incident beam so that the incident beam after passing through the focusing lens can be focused sequentially onto different micromirrors in the MEMS micromirror array. The testing system can calculate the deflection angle of each micromirror based on the light intensity information of the reflected beam detected by the detection module.

6. The system for testing the deflection angle of a micro-mirror in a MEMS micro-mirror array according to claim 1, wherein, The effective aperture of the beam splitter is less than or equal to 70% of the incident beam aperture; and / or, The reflectivity of the beam splitter is 70% to 90%.

7. The testing system for the deflection angle of micromirrors in a MEMS micromirror array according to claim 1, characterized in that, The testing system also includes a light-absorbing box, which is located on the beam path of the incident beam reflected by the beam splitter.

8. The testing system for the deflection angle of micromirrors in a MEMS micromirror array according to claim 1, characterized in that, The detection module includes a detection lens and a detection mechanism. The detection lens is used to focus the reflected light beam onto the detection mechanism, and the detection mechanism is used to detect the light intensity information of the reflected light beam.

9. The testing system for the deflection angle of micromirrors in a MEMS micromirror array according to claim 8, characterized in that, The testing institutions include: A photodiode is used to convert light signals into electrical signals. A transimpedance amplifier, connected to the photodiode, is used to convert the current signal into an amplified voltage signal; An analog-to-digital converter, connected to the transimpedance amplifier, is used to convert a voltage signal into a digital voltage signal; The central processing unit, connected to the analog-to-digital converter, is used to receive the digital voltage signal transmitted by the analog-to-digital converter to obtain the digital amplitude of the digital voltage signal, which is the light intensity information.

10. The testing system for the deflection angle of micromirrors in a MEMS micromirror array according to claim 1, characterized in that, The aperture of the incident beam focused by the focusing lens is smaller than the aperture of the micromirrors in the MEMS micromirror array.

Images