Miniaturized ultrathin imaging system and preparation method thereof

Abstract

The invention provides a miniaturized ultrathin imaging system based on annular aperture imaging and a preparation method thereof, devices of the system comprise an annular aperture ultrathin lens, an automatic focusing direct drive motor, a CMOS detection chip, a flexible circuit board and the like, and high-resolution imaging under strong volume constraint, wide spectral range and large working distance is realized. The manufacturing method of the annular aperture objective lens can realize high-precision, low-cost and batch production of the ultrathin imaging lens.

Description

Technical Field

[0001] The present invention relates to the field of visible light imaging, and in particular to a miniaturized ultra-thin imaging system based on annular aperture imaging and a preparation method thereof. Background Art

[0002] Photoelectric detection equipment is the core sensor of micro-unmanned platforms, which determines the real-time perception and recognition capabilities of unmanned platforms in complex environments. Limited by the small load capacity of micro-unmanned platforms, it is urgent to study miniaturized, lightweight, and low-power optical frequency intelligent perception platforms. The annular aperture ultra-thin imaging system is a new type of thin and light imaging optical system. Compared with conventional optical systems, the annular aperture ultra-thin imaging system has the characteristics of short total length, light weight, and high resolution. Its structure is similar to that of traditional reflective optical systems. It consists of multiple concentric circular ring reflective surfaces processed on the front and back surfaces of a base material. Light enters the system through the incident ring belt, is reflected multiple times by the reflector, and is finally imaged on the detector. Therefore, when the focal length is constant, the system length of the annular aperture is significantly smaller than that of the traditional optical system.

[0003] However, since the annular aperture ultra-thin imaging system is composed of only a single substrate material, it is impossible to achieve achromatic aberration, which seriously affects the imaging quality. At the same time, the surface shape of the annular aperture lens is very complex compared to the traditional transmission lens. Conventional surface processing methods are difficult to meet its surface accuracy requirements. In addition, there are both transmission-type annular zones and reflection-type annular zones on the same surface. Conventional coating evaporation methods cannot distinguish between different annular zones. It is also difficult to achieve millimeter-level annular zone sizes using split coating or masking methods, which places extremely high demands on the coating process. Therefore, an effective and easy-to-implement method is needed to realize the production of annular aperture objective lenses. Summary of the invention

[0004] Purpose of the present invention The present invention provides a system, working mode, and manufacturing method for a miniaturized imaging system under strong volume constraints that overcomes the above-mentioned problems or at least partially solves the above-mentioned problems.

[0005] Specifically, the present invention application provides a miniaturized ultra-thin imaging system based on annular aperture imaging and a manufacturing method thereof.

[0006] On the first aspect, the present application proposes a miniaturized ultra-thin imaging system based on annular aperture imaging, which imaging system includes an annular aperture ultra-thin lens, an autofocus direct-drive motor, a CMOS detection chip, a flexible circuit board, etc., and is characterized in that the annular aperture ultra-thin lens includes an annular aperture objective lens and a diffraction window formed by etching a diffraction element on the exit window of the annular aperture objective lens.

[0007] Furthermore, the annular aperture ultra-thin lens, under strong volume constraints, compresses the length of the imaging light path by folding the light path in a limited space, and corrects the chromatic aberration caused by imaging a wide spectral range with a single substrate material through a diffraction window.

[0008] Furthermore, the autofocus direct-drive motor and driver are integrated inside the system, and complete precise autofocus of targets within a large working distance range through a built-in microcontroller, and drive the intercept between the annular aperture ultra-thin lens and the CMOS detection chip through a voice coil motor; the built-in microcontroller reads the information required for autofocus from the CMOS detection chip, calculates and searches for the best focus position, and drives the direct-drive motor to drive the annular aperture ultra-thin lens to the correct focus position, thereby achieving fast autofocus.

[0009] Furthermore, the CMOS detection chip detects light signals, and the detector chip adopts a small pixel back-illuminated design and can achieve adaptive exposure control.

[0010] Furthermore, the CMOS detection chip adopts a small pixel back-illuminated design and can realize adaptive exposure control. Its working process includes: power on, pull ResetB low, reset the CMOS chip, and pull PWDN high; power on DOVDD and AVDD. If they cannot be powered on at the same time, DOVDD must be powered on first and AVDD must be powered on later; after AVDD is stable for 5ms, pull PWDN low; after PWDN is set low for 1ms, pull ResetB high; after waiting for 20ms, complete the system power-on; initialize SCCB register settings, configure CMOS control pins, and configure working modes; configure the modes and multiplexing functions of related pins, and enable clocks; configure DCMI related settings; configure DMA; set image output Small, enable DCMI capture; autofocus, release the motor to the initial position; obtain the preview image from the CMOS sensor; calculate and drive the motor to drive the lens to the specified focus position; repeat until a good preview image is obtained; pause autofocus and keep the lens in the correct focus position; image acquisition, read preview parameters; read shooting setting parameters; convert preview gain and exposure values ​​to photo gain and exposure values; after waiting for two Vsyncs, grab the third frame of image; write preview setting parameters and restart autofocus; shut down the system and pull down XCLK; cut off AVDD, DVDD and DOVDD. If they cannot be cut off at the same time, DVDD must be cut off first, AVDD second, and DOVDD last; pull down PWDN and RESETB.

[0011] Furthermore, the flexible circuit board is used to process the acquired image data, realize the transmission of clock signals and data signals through a serial control bus, and output images through a digital video interface.

[0012] Furthermore, the flexible printed circuit board realizes the transmission of clock signals and data signals through a serial control bus, and outputs images through a digital video interface; the serial control bus uses the SCCB transmission protocol, which is similar to the IIC protocol: when IIC transmits each byte, the party receiving the data must send one bit of confirmation data; while SCCB transmits 9 bits of data at a time, the first 8 bits are useful data, and the 9th bit of data is a don't care bit in the write cycle and is an NA bit in the read cycle.

[0013] Furthermore, SCCB defines the basic unit of data transmission as phase, that is, one phase transmits one byte of data; the clock signal, the system's image data output is carried out under the control of PCLK, VSYNC and HREF / HSYNC, where PCLK is the pixel clock, one PCLK clock outputs one pixel (or half a pixel); VSYNC is the frame synchronization signal; HREF / HSYNV is the line synchronization signal; the data signal, the image data is output when HREF is high, when HREF becomes high, each PCLK clock outputs an 8-bit data, each PCLK outputs one byte, and in the RGB / YUV output format, each tp=2 Tpclk, if it is in raw format, then one tp=1 Tpclk.

[0014] In a second aspect, the present application provides a method for manufacturing an annular aperture ultra-thin lens, comprising: using ultra-precision CNC continuous trajectory to process the surface shape of an annular aperture objective lens; using ion evaporation to fully coat the front and back surfaces of the annular aperture objective lens with a metal film; and using femtosecond laser etching to remove the window rings on the front and back surfaces of the annular aperture objective lens.

[0015] Furthermore, the method of using ultra-precision CNC continuous trajectory to process the annular aperture objective lens surface shape comprises: obtaining a cylindrical prototype embryo for the annular aperture objective lens processing by laser cutting a magnesium fluoride plane material plate; cleaning and polishing the prototype embryo to make it basically conform to the cubic scale before processing; fixing the prototype embryo by a precision clamping tool; positioning the precision tool at the center of the processing table by a four-axis translation stage to ensure that the central axis of the prototype embryo is at the origin position and perpendicular to the processing table; inputting the surface shape data of the front surface of the annular aperture objective lens into an ultra-precision CNC continuous trajectory processing machine tool, and performing Perform front surface profiling; use a high-precision contour measuring instrument to measure the surface of the annular aperture objective lens to check whether the surface error meets the accuracy requirements; flip the precision clamping tooling, and again position the precision tooling at the center of the processing table through the four-axis translation stage to ensure that the center axis of the prototype embryo is at the origin and perpendicular to the processing table; input the rear surface profile data of the annular aperture objective lens into the ultra-precision CNC continuous trajectory machining machine tool to perform rear surface profiling; use a high-precision contour measuring instrument to measure the surface of the annular aperture objective lens to check whether the surface error meets the accuracy requirements.

[0016] Furthermore, the method of using ion evaporation to fully coat the front and rear surfaces of the annular aperture objective lens with a metal film includes: cleaning before coating, inspection after cleaning, and coating.

[0017] Furthermore, the cleaning before coating includes: wearing clean gloves; picking up the outer circle of the part with tweezers, and wiping the part with a dust-free cloth dipped in anhydrous ethanol; clamping the part on the cleaning tool (vertically placed), soaking it in a beaker filled with acetone, soaking for 5 minutes, and taking it out; soaking the cleaning tool with the part clamped in a beaker filled with anhydrous ethanol, soaking for 5 minutes, and taking it out; rinsing the parts and the tool with deionized water for 10 to 30 seconds, and rinsing in a beaker filled with deionized water for 5 to 10 seconds; repeating this step 3 times; soaking the cleaning tool with the part clamped in a beaker filled with deionized water, rinsing for 30 seconds, taking it out, and rinsing it with deionized water; repeating this step 3 times; rinsing the parts with anhydrous ethanol, blowing them dry with nitrogen, and putting them in a part turnover box; checking the surface of the parts, and confirming that there are no dirty spots before switching to the coating procedure;

[0018] The post-cleaning inspection is to observe the cleaned parts under a 10× magnification microscope. If there are no obvious marks or patches of dirty spots, the coating process is carried out.

[0019] The coating process includes: turning on the main power supply of the coating machine and each control power supply, and the indicator light indicates that the equipment is in normal working state or standby state; checking whether the water and gas provided by the coating machine meet the process requirements; calibrating the deposition rate; running the coating process program to control the coating equipment and realize full automation of the coating process; after the coating program is executed, filling the vacuum chamber with nitrogen to restore it to normal pressure; opening the vacuum chamber door, removing the coating fixture from the workpiece disk, and placing it on the clean bench; removing the parts from the fixture and packing them in a ziplock bag.

[0020] Furthermore, the deposition rate correction is to correct the deposition rate of the film layer before coating in order to accurately control the film thickness, including: using a flat quartz glass as a substrate, half of which is taped, coating a single layer of Al film, and setting the coating time tC (tC=10min); after the coating is completed, the tape is torn off to form a step; the step surface height dC of the single Al film is measured using a profilometer; the deposition rate V is calculated according to the formula: VC=dC / tC.

[0021] Furthermore, the use of femtosecond laser etching to remove the window annular zones on the front and rear surfaces of the annular aperture objective lens includes: cleaning, laser film removal, and processing result detection;

[0022] The cleaning mentioned above requires cleaning the sample before laser processing to remove surface dirt.

[0023] The laser film removal uses a femtosecond laser to remove the metal film of the designated window ring band, including: turning on the power of the equipment and the laser, running the laser cooling water tank, turning on the laser control software, turning on the laser, and after completion, the machine needs to be warmed up for 30 minutes before processing; sample clamping: installing the lens to be filmed in a customized fixture, fixing the fixture on the XY displacement table of the processing platform, and ensuring that the sample is fixed and does not shake; visual positioning: adjusting the sample position and the height of the laser processing head so that the sample can be clearly imaged within the field of view of the visual CCD, using the visual positioning software to grasp and position the sample contour, and positioning the sample center at the exact center of the laser processing head; processing drawing setting: importing the sample drawing into the laser processing software, filling the area to be processed in the drawing for the ring band to be removed on the current surface, and setting the filling spacing; laser processing: setting the laser power, frequency, galvanometer scanning speed, and number of scans, starting processing, turning the sample over after completing the single-sided processing, and repeating the visual positioning and laser processing process to achieve the removal of the double-sided film layer of the sample;

[0024] The processing result detection is characterized in that the center and edge ring bands on the front and back sides of the sample are laser removed respectively, and a microscope is used to detect whether the laser removed area is accurately positioned and removed cleanly without residue.

[0025] The present invention application provides a miniaturized ultra-thin imaging system based on annular aperture imaging and a preparation method thereof. The system includes an annular aperture ultra-thin lens, an autofocus direct drive motor, a CMOS detection chip, a flexible circuit board, etc., to achieve high-resolution imaging under strong volume constraints, a wide spectral range, and a large working distance. The present invention application can be applied to a micro-unmanned platform to achieve chip-level "plug and play" and low system-dependent detection perception and information processing; the use of refractive-diffractive hybrid annular aperture imaging can achieve high-quality detection of long-distance targets under strong volume constraints; the autofocus direct drive motor can achieve adaptive focusing within a large working distance range; the annular aperture objective lens manufacturing method can achieve high-precision, low-cost, and mass production of ultra-thin imaging lenses. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 A schematic diagram of the principle of a miniaturized ultra-thin imaging system based on annular aperture imaging provided by the present invention;

[0028] Figure 2A flow chart of a method for manufacturing an annular aperture ultra-thin lens provided in the present invention;

[0029] Figure 3 A flow chart of an ultra-precision CNC continuous trajectory machining method provided by the present invention;

[0030] Figure 4 A flow chart of a method for coating the front and rear surfaces of an annular aperture objective lens with a metal film by ion evaporation provided by the present invention;

[0031] Figure 5 A flow chart of a method for removing window annular zones on the front and rear surfaces of an annular aperture objective lens by femtosecond laser etching provided in the present invention. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the embodiments of the present invention application clearer, the technical solution in the embodiments of the present invention application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention application. Obviously, the described embodiments are part of the embodiments of the present invention application, not all of the embodiments. It should be noted that, in the absence of conflict, the various features in the embodiments of the present invention application can be combined with each other, and the combined embodiments are still within the protection scope of the present invention application.

[0033] In the description of the present invention application, it should be noted that, unless otherwise specified and limited, the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate the orientation or position relationship based on the orientation or position relationship shown in the drawings, or the orientation or position relationship in which the product of the application is usually placed when in use, which is only for the convenience of describing the present invention application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention application. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0034] In the description of the present invention application, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention application can be understood according to specific circumstances.

[0035] The specific implementation methods of the present invention are further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0036] Attached Figure 1 A schematic diagram of the principle of a miniaturized ultra-thin imaging system based on annular aperture imaging provided in the present invention application, the imaging system comprises an annular aperture ultra-thin lens, an autofocus direct drive motor (2), a CMOS detection chip (3), a flexible circuit board (4), etc., wherein the annular aperture ultra-thin lens comprises an annular aperture objective lens (11) and a diffraction window (12).

[0037] The annular aperture ultra-thin lens is used to compress the length of the imaging optical path by folding the optical path in a limited space under a strong volume constraint, has a smaller space size and weight, and ensures good imaging resolution to meet the needs of long-distance detection; and corrects the chromatic aberration caused by imaging a wide spectral range with a single substrate material through a diffraction window, comprising an annular aperture objective lens (11) and a diffraction window (12); the annular aperture objective lens (11) is used to realize optical imaging, based on a magnesium fluoride substrate material, and uses four reflections to realize imaging optical path folding, and has a focal length of 4.5 mm, a thickness of only 1.6 mm, an aperture of 3.8 mm, and a back intercept of 200 μm; since the system is composed of only a single substrate material, all internal reflections occur inside the material constituting the annular aperture objective lens, and for imaging in a wide spectral range, the system cannot achieve achromatic aberration, while the diffraction element has special dispersion properties and thin element properties, and can eliminate the influence of chromatic aberration without increasing the complexity of the system, thereby achieving high-quality imaging. In order to further reduce the volume of the system, the diffraction element is etched on the exit window of the annular aperture objective lens to form a diffraction window (12).

[0038] The autofocus direct-drive motor (2) drives the intercept between the annular aperture ultra-thin lens and the CMOS detection chip (3) through a voice coil motor, and realizes fast autofocus through an adaptive search algorithm; the direct-drive motor driver is integrated inside the system, and completes autofocus through a built-in microcontroller, with a focus range of ±0.5mm; the internal thread of the motor is M5.5mm, which can support ultra-thin lenses with a maximum diameter of no more than 5mm.

[0039] The CMOS detection chip (3) adopts a small pixel back-illuminated design and can realize adaptive exposure control. The pixel size is 1.4 μm, the maximum resolution can support 2593×1944, and the frame rate can reach 60 FPS at 720p.

[0040] The flexible circuit board (4) transmits clock signals and data signals through a serial control bus, and outputs images through a digital video interface. The serial control bus uses an SCCB transmission protocol to transmit 9 bits of data at a time, the first 8 bits are useful data, and the 9th bit of data is a don't care bit in a write cycle and an NA bit in a read cycle. The system's image data output is performed under the control of PCLK, VSYNC and HREF / HSYNC, wherein PCLK is a pixel clock, and one PCLK clock outputs one pixel (or half a pixel); VSYNC is a frame synchronization signal; HREF / HSYNV is a line synchronization signal; and data signal, image data is output when HREF is high. When HREF becomes high, one 8-bit data is output for each PCLK clock, and one byte is output for each PCLK clock. In the RGB / YUV output format, each tp=2 Tpclks. If it is a raw format, one tp=1 Tpclk.

[0041] Attached Figure 2 The present invention provides a method for manufacturing an annular aperture ultra-thin lens, comprising the steps of: 201, processing the annular aperture objective lens surface; 202, coating the entire surface with a metal film; 203, removing the surface window ring zone.

[0042] Among them, the annular aperture objective lens surface is processed by using ultra-precision CNC continuous trajectory, as shown in the attached Figure 3The flow chart of the ultra-precision CNC continuous trajectory processing method shown in the figure includes the following steps: 301, flat material cutting, by laser cutting a flat material plate (magnesium fluoride), to obtain a cylindrical prototype blank for annular aperture objective lens processing; 302, prototype blank cleaning and polishing, the prototype blank is cleaned and polished to make it basically meet the cubic scale before processing; 303, prototype blank clamping and fixing, the prototype blank is fixed by a precision clamping tool; 304, prototype blank table positioning, the precision tool is positioned at the center of the processing table by a four-axis translation stage, to ensure that the center axis of the prototype blank is at the origin position and perpendicular to the processing table; 305, CNC surface profile processing, the front surface profile data of the annular aperture objective lens is input into the ultra-precision CNC continuous trajectory processing machine tool, and the front surface profile processing is performed; 306, surface profile measurement, so that The surface of the annular aperture objective lens is measured by a high-precision contour measuring instrument to check whether the surface error meets the accuracy requirement; 307. The processed surface is turned over. After the front surface of the prototype embryo is processed through steps 304-306, the precision clamping tooling is turned over to process the rear surface of the prototype embryo; processing the rear surface of the prototype embryo includes processing the rear surface of the prototype embryo through steps 304-step 306, 304. The precision tooling is positioned at the center of the processing table by the four-axis translation stage again to ensure that the central axis of the prototype embryo is at the origin and perpendicular to the processing table; 305. The surface data of the rear surface of the annular aperture objective lens is input into the ultra-precision CNC continuous trajectory processing machine tool to process the rear surface; 306. The surface of the annular aperture objective lens is measured by a high-precision contour measuring instrument to check whether the surface error meets the accuracy requirement.

[0043] The steps of fully coating the surface of the annular aperture objective lens with a metal film after processing the surface shape of the annular aperture objective lens, using ion evaporation to fully coat the front and rear surfaces of the annular aperture objective lens with a metal film include: 401-407 cleaning before coating, 408 inspection after cleaning, and 409-413 coating; the process is as shown in the attached Figure 4 shown.

[0044] Cleaning before coating includes: 401. Preparation before cleaning, wear clean gloves; 402. Wipe with dust-free cloth, pick up the outer circle of the part with tweezers, and wipe the part with dust-free cloth dipped in anhydrous ethanol; 403. Clamp the part, clamp the part on the cleaning tool (vertically placed); 404. Acetone soak for 5 minutes, soak the cleaning tool with the clamped part in a beaker filled with acetone, soak for 5 minutes, and take it out; 405. Anhydrous ethanol soak for 5 minutes, soak the cleaning tool with the clamped part in a beaker filled with anhydrous ethanol. 406. Rinse with deionized water. Rinse the parts and tooling with deionized water for 10 to 30 seconds, and rinse in a beaker of deionized water for 5 to 10 seconds, and repeat 3 times; immerse the cleaning tooling with parts in a beaker of deionized water, rinse for 30 seconds, take out, rinse with deionized water, and repeat 3 times; 407. Blow dry with nitrogen. Rinse the parts with anhydrous ethanol, blow dry with nitrogen, and put them in the parts turnover box; check the surface of the parts, and transfer to the coating procedure after confirming that there are no dirty spots.

[0045] 408. Inspection after cleaning: observe the cleaned parts under a 10× microscope. If there are no obvious marks or dirty spots, proceed to the coating process.

[0046] 409-413 coating process, including: 409, start and check the coating machine, turn on the main power of the coating machine and each control power supply, the indicator light indicates the normal working state or standby state of the equipment, check whether the water and gas supporting the coating machine meet the process requirements; 410, deposition rate correction; 411, start the coating program, run the coating process program to control the coating equipment, and realize the full automation of the coating process; 412, fill with nitrogen to restore to normal pressure, after the coating program is executed, fill the vacuum chamber with nitrogen to restore to normal pressure; 413, coating sample inspection, open the vacuum chamber door, remove the coating fixture from the workpiece plate, place it on the clean bench, remove the parts from the fixture, and pack them in ziplock bags.

[0047] Before coating, the deposition rate of the film layer needs to be calibrated in order to accurately control the film thickness. Step 410 is to calibrate the deposition rate, including: using a flat quartz glass as a substrate, half of which is taped, coating a single layer of Al film, and setting a coating time tC (tC=10min); after coating, the tape is torn off to form a step; a profilometer is used to measure the step surface height dC of the single Al film; and the deposition rate V is calculated according to the formula: VC=dC / tC.

[0048] In addition, after the surface is fully coated with metal film, step 203 removes the surface window ring zone, and uses femtosecond laser etching to remove the front and rear surface window ring zones of the annular aperture objective lens, including steps: 501 cleaning, 502-506 laser film removal, and 507 processing result detection. The process is as shown in the attached figure. Figure 5 As shown:

[0049] Among them, 501, cleaning, the sample needs to be cleaned before laser processing to remove surface dirt;

[0050] Using a femtosecond laser to remove the metal film in the designated window ring zone includes the following steps: 502, starting the laser, turning on the equipment and the laser power supply, running the laser cooling water tank, opening the laser control software, and starting the laser. After completion, the machine needs to be warmed up for 30 minutes before processing can be performed; 503, sample clamping, installing the lens to be film-removed in a customized fixture, and fixing the fixture on the XY displacement stage of the processing platform to ensure that the sample is fixed and does not shake; 504, visual positioning, adjusting the sample position and the height of the laser processing head so that the sample can be clearly imaged on the visual CCD Within the field of view, use the visual positioning software to grab and locate the sample outline, and locate the center of the sample at the exact center of the laser processing head; 505, processing drawing setting, import the sample drawing into the laser processing software, and fill the area to be processed in the drawing for the ring band to be removed on the current surface, and set the filling spacing; 506, laser processing, set the laser power, frequency, galvanometer scanning speed, and number of scans, start processing, turn the sample over after completing single-sided processing, and repeat the visual positioning and laser processing process to achieve the removal of the double-sided film layer of the sample.

[0051] Step 507, processing result detection, includes laser removal of the center and edge ring bands on both sides of the sample, and using a microscope to detect whether the laser removal area is accurately positioned and removed cleanly without residue.

[0052] It is understandable that the currently published visible light imaging systems often use multi-piece spherical / aspherical transmission types. Under strong volume constraints, it is difficult to simultaneously meet the requirements of long working distance and small volume; compared with a few super-lenses or micro-structure plane phase modulation designed with super-surfaces, its imaging quality and resolution are difficult to meet the requirements of long-distance detection. At the same time, the surface shape of the annular aperture lens is very complex compared to the traditional transmission lens. Conventional surface processing methods are difficult to meet its surface accuracy requirements. In addition, there are both transmission-type annular zones and reflection-type annular zones on the same surface. Conventional coating evaporation methods cannot distinguish between different annular zones. It is also difficult to achieve millimeter-level annular zone sizes using split coating or masking methods, which places extremely high demands on the coating process.

[0053] According to the technical problem to be solved by the present invention, the present invention provides a highly integrated micro-detection system and manufacturing method, which realizes high-resolution imaging under strong volume constraints, wide spectral range, and large working distance. The use of refractive-diffractive hybrid annular aperture imaging can realize high-quality detection of long-distance targets under strong volume constraints; the autofocus direct-drive motor can realize adaptive focusing within a large working distance range; the annular aperture objective lens manufacturing method can realize high-precision, low-cost, and mass production of ultra-thin imaging lenses.

[0054] The above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them. Those skilled in the art should understand that although the present invention has been disclosed as a preferred embodiment, the embodiments are not used to limit the present invention. Any equivalent changes or modifications made without departing from the spirit and scope of the present invention also belong to the protection scope of the present invention.

Claims

1. A miniaturized ultra-thin imaging system based on annular aperture imaging, the imaging system comprising an annular aperture ultra-thin lens, an autofocus direct drive motor (2), a CMOS detection chip (3), a flexible circuit board (4), etc., characterized in that: The annular aperture ultra-thin lens comprises an annular aperture objective lens (11) and a diffraction window (12) formed by etching a diffraction element on an exit window of the annular aperture objective lens.

2. A miniaturized ultra-thin imaging system based on annular aperture imaging according to claim 1, characterized in that: The annular aperture ultra-thin lens compresses the length of the imaging optical path by folding the optical path in a limited space under a strong volume constraint, and corrects the chromatic aberration caused by imaging a wide spectral range with a single substrate material through a diffraction window.

3. A miniaturized ultra-thin imaging system based on annular aperture imaging according to claim 1, characterized in that: The autofocus direct drive motor and the driver are integrated inside the system, and the built-in microcontroller is used to achieve accurate autofocus of targets within a large working distance range, and the voice coil motor is used to drive the intercept between the annular aperture ultra-thin lens and the CMOS detection chip; The built-in microcontroller reads the information required for autofocus from the CMOS detection chip, calculates and searches for the best focus position, and drives the direct-drive motor to drive the annular aperture ultra-thin lens to the correct focus position to achieve fast autofocus.

4. The miniaturized ultra-thin imaging system based on annular aperture imaging according to claim 1, characterized in that: The CMOS detection chip detects light signals. The detector chip adopts a small pixel back-illuminated design and can realize adaptive exposure control.

5. The miniaturized ultra-thin imaging system based on annular aperture imaging according to claim 4, characterized in that: The CMOS detection chip adopts a small pixel back-illuminated design and can realize adaptive exposure control. Its working process includes: power on, pull down ResetB, reset the CMOS chip, and pull up PWDN; power on DOVDD and AVDD. If they cannot be powered on at the same time, DOVDD must be powered on first and AVDD must be powered on later; after AVDD is stable for 5ms, pull down PWDN; after PWDN is set low for 1ms, pull up ResetB; after waiting for 20ms, complete the system power-on; initialize SCCB register settings, configure CMOS control pins, and configure working modes; configure the modes and multiplexing functions of related pins, enable clocks; configure DCMI related settings; configure DMA; set image output size, Enable DCMI capture; autofocus, release the motor to the initial position; obtain the preview image from the CMOS sensor; calculate and drive the motor to drive the lens to the specified focus position; repeat until a good preview image is obtained; pause autofocus and keep the lens in the correct focus position; image acquisition, read preview parameters; read shooting setting parameters; convert preview gain and exposure values ​​to photo gain and exposure values; wait for two Vsyncs, grab the third frame of image; write preview setting parameters, restart autofocus; shut down the system, pull down XCLK; cut off AVDD, DVDD and DOVDD. If they cannot be cut off at the same time, DVDD must be cut off first, AVDD second, and DOVDD last; pull down PWDN and RESETB.

6. The miniaturized ultra-thin imaging system based on annular aperture imaging according to claim 1, characterized in that: The flexible circuit board is used to process the acquired image data, realize the transmission of clock signal and data signal through the serial control bus, and output the image through the digital video interface.

7. A miniaturized ultra-thin imaging system based on annular aperture imaging according to claim 6, characterized in that: The flexible circuit board realizes the transmission of clock signal and data signal through the serial control bus, and outputs the image through the digital video interface; the serial control bus uses the SCCB transmission protocol, which is similar to the IIC protocol: when the IIC transmits each byte, the party receiving the data must send one bit of confirmation data; while the SCCB transmits 9 bits of data at a time, the first 8 bits are useful data, and the 9th bit of data is a don't care bit in the write cycle and is an NA bit in the read cycle.

8. The miniaturized ultra-thin imaging system based on annular aperture imaging according to claim 7, characterized in that: SCCB defines the basic unit of data transmission as phase, that is, one phase transmits one byte of data; the clock signal, the system's image data output is carried out under the control of PCLK, VSYNC and HREF / HSYNC, where PCLK is the pixel clock, one PCLK clock outputs one pixel (or half a pixel); VSYNC is the frame synchronization signal; HREF / HSYNV is the line synchronization signal; the data signal, the image data is output when HREF is high, when HREF becomes high, each PCLK clock outputs an 8-bit data, each PCLK outputs one byte, and in the RGB / YUV output format, each tp = 2 Tpclk, if it is in raw format, then one tp = 1 Tpclk.

9. A method for manufacturing an annular aperture ultra-thin lens, comprising: Use ultra-precision CNC continuous trajectory to process the annular aperture objective lens surface; Ion evaporation is used to fully coat the front and back surfaces of the annular aperture objective lens with a metal film; Femtosecond laser etching was used to remove the window rings on the front and back surfaces of the annular aperture objective.

10. The method for manufacturing an annular aperture ultra-thin lens according to claim 9, characterized in that: The method of using ultra-precision CNC continuous trajectory to process the annular aperture objective lens surface shape comprises: cutting a magnesium fluoride plane material plate by laser to obtain a cylindrical prototype embryo for processing the annular aperture objective lens; cleaning and polishing the prototype embryo to make it basically conform to the cubic scale before processing; fixing the prototype embryo by a precision clamping tool; positioning the precision tool at the center of the processing table by a four-axis translation stage to ensure that the central axis of the prototype embryo is at the origin position and perpendicular to the processing table; inputting the surface shape data of the front surface of the annular aperture objective lens into an ultra-precision CNC continuous trajectory processing machine tool to process the front surface Surface profiling; Use a high-precision contour measuring instrument to measure the surface profile of the annular aperture objective lens to check whether the surface error meets the accuracy requirements; Flip the precision clamping tooling, and again position the precision tooling at the center of the processing table through the four-axis translation stage to ensure that the center axis of the prototype embryo is at the origin and perpendicular to the processing table; Input the surface profile data of the rear surface of the annular aperture objective lens into the ultra-precision CNC continuous trajectory processing machine tool to perform rear surface profiling; Use a high-precision contour measuring instrument to measure the surface profile of the annular aperture objective lens to check whether the surface error meets the accuracy requirements.

11. The method for manufacturing an annular aperture ultra-thin lens according to claim 9, characterized in that: The method of using ion evaporation to fully coat the front and rear surfaces of the annular aperture objective lens with a metal film comprises: cleaning before coating, inspection after cleaning, and coating.

12. The method for manufacturing an annular aperture ultra-thin lens according to claim 11, characterized in that: The cleaning before coating includes: wearing clean gloves; picking up the outer circle of the part with tweezers, and wiping the part with a dust-free cloth dipped in anhydrous ethanol; clamping the part on the cleaning tool (vertically placed), soaking it in a beaker filled with acetone, soaking for 5 minutes, and taking it out; soaking the cleaning tool with the part clamped in a beaker filled with anhydrous ethanol, soaking for 5 minutes, and taking it out; rinsing the parts and tool with deionized water for 10 to 30 seconds, and rinsing in a beaker filled with deionized water for 5 to 10 seconds; repeating this step 3 times; soaking the cleaning tool with the part clamped in a beaker filled with deionized water, rinsing for 30 seconds, taking it out, and rinsing it with deionized water; repeating this step 3 times; rinsing the parts with anhydrous ethanol, blowing them dry with nitrogen, and putting them in a part turnover box; checking the surface of the parts, and confirming that there are no dirty spots before switching to the coating procedure; The post-cleaning inspection is to observe the cleaned parts under a 10× magnification microscope. If there are no obvious marks or patches of dirty spots, the coating process is carried out. The coating process includes: turning on the main power supply of the coating machine and each control power supply, and the indicator light indicates that the equipment is in normal working state or standby state; checking whether the water and gas provided by the coating machine meet the process requirements; calibrating the deposition rate; running the coating process program to control the coating equipment and realize full automation of the coating process; after the coating program is executed, filling the vacuum chamber with nitrogen to restore it to normal pressure; opening the vacuum chamber door, removing the coating fixture from the workpiece disk, and placing it on the clean bench; removing the parts from the fixture and packing them in a ziplock bag.

13. The method for manufacturing an annular aperture ultra-thin lens according to claim 12, characterized in that: The deposition rate correction mentioned above requires that the deposition rate of the film layer be corrected before coating in order to accurately control the film thickness, including: using a flat quartz glass as a substrate, half of which is taped, coating a single layer of Al film, and setting the coating time tC (tC = 10 min); after the coating is completed, the tape is torn off to form a step; the height dC of the step surface of the single Al film is measured using a profilometer; the deposition rate V is calculated according to the formula: VC=dC / tC.

14. The method for manufacturing an annular aperture ultra-thin lens according to claim 9, characterized in that: The method of using femtosecond laser etching to remove the window annular zones on the front and rear surfaces of the annular aperture objective lens includes: cleaning, laser film removal, and processing result detection; The cleaning mentioned above requires cleaning the sample before laser processing to remove surface dirt. The laser film removal uses a femtosecond laser to remove the metal film of the designated window ring band, including: turning on the power of the equipment and the laser, running the laser cooling water tank, turning on the laser control software, turning on the laser, and after completion, the machine needs to be warmed up for 30 minutes before processing; sample clamping: installing the lens to be filmed in a customized fixture, fixing the fixture on the XY displacement table of the processing platform, and ensuring that the sample is fixed and does not shake; visual positioning: adjusting the sample position and the height of the laser processing head so that the sample can be clearly imaged within the field of view of the visual CCD, using the visual positioning software to grasp and position the sample contour, and positioning the sample center at the exact center of the laser processing head; processing drawing setting: importing the sample drawing into the laser processing software, filling the area to be processed in the drawing for the ring band to be removed on the current surface, and setting the filling spacing; laser processing: setting the laser power, frequency, galvanometer scanning speed, and number of scans, starting processing, turning the sample over after completing the single-sided processing, and repeating the visual positioning and laser processing process to achieve the removal of the double-sided film layer of the sample; The processing result detection is characterized in that the center and edge ring bands on the front and back sides of the sample are laser removed respectively, and a microscope is used to detect whether the laser removed area is accurately positioned and removed cleanly without residue.

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