High-fault-tolerance compact imaging system and preparation method thereof

Abstract

The invention discloses a high-fault-tolerance compact imaging system and a preparation method thereof, and belongs to an optical imaging technology. The high-fault-tolerance compact imaging system comprises a conjugate lens, a main camera lens and an imaging surface element which are sequentially arranged from a shot object side along an optical axis; the micro-motion mechanisms are respectively configured for the conjugate lens and the main shooting lens; the micro-motion mechanism of the conjugate lens is configured to enable the conjugate lens to move for a micro-motion range db along the optical axis, and the micro-motion mechanism of the main camera lens is configured to enable the main camera lens to move for a micro-motion range da along the optical axis, so that a shot object can still form a clear image on the imaging surface element in a movable range D; according to the imaging system, the fault-tolerant capability of the whole optical system can be improved, and the focusing speed and precision of the optical system are remarkably improved.

Description

Technical Field

[0001] The invention relates to optical imaging technology, in particular to a high fault-tolerant compact imaging system and a preparation method thereof. Background Art

[0002] Compact optical systems generally include smartphones with a light source, a single camera, and a computer processor, or a module formed by an independent camera module, an independent light source, an independent filter, an independent lens, or an integrated camera, light source, filter, and lens to provide a field of view for camera observation. The camera module usually includes a conjugate lens, a main camera lens, and an imaging plane. The object distance must be within the focal length of the conjugate lens so that the light can continue to enter the main camera lens as parallel light after passing through the conjugate lens and form an enlarged real image on the imaging plane.

[0003] Compact optical systems are generally used to shoot objects of 0.5-10.0 microns in size, and the object distance lens group is usually in the range of 0.2 to 10.0 mm for ultra-close imaging. In this type of optical system, in order to obtain good image quality, the distance from the object to the imaging component must fall exactly within a very limited object distance range (0.2 to 10.0 mm), that is, only within a given object distance range can a high image quality be achieved, and beyond this range, an accurate image cannot be obtained, and the error tolerance is small; different optical systems and modules may fail to focus or require fine-tuning of the actual object distance and image distance to achieve effective focus due to parts and assembly tolerances and lens manufacturing differences; and because the entire optical path component is highly sensitive to size (50μm level), in later use, the focus may fail due to material aging, vibration, temperature changes, humidity changes, etc., and need to be returned to the factory for repair. To address these issues, the current fine-tuning methods include: (1) adding or reducing one or more 50μm thick gaskets; (2) replacing lenses; (3) using high-precision processing methods to reduce part manufacturing tolerances; (4) using tight fixtures to improve assembly accuracy; and (5) interchanging components or reassembling.

[0004] In general, existing compact optical systems and modules have poor fault tolerance in focusing capabilities, and have disadvantages such as the need to adjust the overall focus, many processes, and slow focusing speed, which affect the actual application efficiency. Summary of the invention

[0005] In view of the above problems existing in the current compact imaging system with micron-level precision, the inventor of this application proposes a high-speed and high-tolerance focusing solution, that is, by moving the conjugate lens and (or) the main camera lens, to automatically compensate for: 1) changes in object distance and image distance caused by component and assembly tolerances; 2) changes in focal length caused by differences in lens quality; 3) system out-of-focus problems caused by other reasons. This solution can improve the fault tolerance of the entire optical system and significantly improve the focusing speed and accuracy of the optical system.

[0006] A first aspect of the present invention provides a highly fault-tolerant compact imaging system, comprising: a conjugate lens, a main camera lens, and an imaging surface element arranged in sequence along the optical axis from the object side;

[0007] It also includes micro-motion mechanisms respectively configured for the conjugate lens and the main camera lens;

[0008] The micro-motion mechanism of the conjugate lens is configured so that the conjugate lens can move along the optical axis within a micro-motion range d b , and the micro-motion mechanism of the main camera lens is configured so that the main camera lens can move along the optical axis within a micro-motion range d a , so that the photographed object can still form a clear image on the imaging surface element within the movable range D.

[0009] Preferably, the highly fault-tolerant compact imaging system further comprises a photographic object holder, which is movable along the optical axis so as to adjust the movement of the photographic object within the movable range D;

[0010] The movable range D of the object holder satisfies the following conditions:

[0011] Keep the relative distance between the object and the conjugate lens at object distance u b ±1 / 2d b range, and

[0012]

[0013] Where: u a and u b Respectively represent the focusing distances of the main lens and the conjugate lens;

[0014] The object distance refers to the distance from the object to the optical center of the conjugate lens, and the range is u b ±1 / 2d b ;

[0015] d b Take the maximum value and substitute it into formula (5) for calculation;

[0016] d a Take the maximum value and substitute it into formula (5) for calculation.

[0017] Preferably, the setting position of the object holder satisfies the following condition: the total distance from the object, the conjugate lens, the main camera lens to the imaging surface element, that is, the longitudinal dimension of the compact imaging system is less than 30.0 mm.

[0018] Preferably, the longitudinal dimension is 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, 22mm, 25mm, or a range between any two of the longitudinal dimension values.

[0019] Preferably, the allowable micro-motion range of the conjugate lens is b It is 10 to 600 microns, 10 to 500 microns, 10 to 400 microns, 10 to 300 microns, 10 to 200 microns or 10 to 100.

[0020] Preferably, the allowable micro-motion range of the main camera lens is a It is 10 to 800 microns, 10 to 700 microns, 10 to 600 microns, 10 to 500 microns, 10 to 400 microns, 10 to 300 microns, 10 to 200 microns or 10 to 100.

[0021] Preferably, in the compact imaging system, the distance from the optical center of the main camera lens to the imaging surface is the distance, and its range is u a ±1 / 2d a .

[0022] Preferably, the object distance is between 0.2 and 10.0 mm, and the image distance is between 0.2 and 10.0 mm.

[0023] Preferably, the object distance is between 0.2 and 5.0 mm, and the image distance is between 0.2 and 5.0 mm.

[0024] The magnification of the compact imaging system is the focal length u of the main camera lens. a The focal distance u from the conjugate lens b The ratio Ua / Ub is 0.5~50.

[0025] Preferably, in any of the above compact imaging systems, the imaging surface element adopts a CCD sensor or a CMOS sensor.

[0026] Preferably, in any of the above-mentioned compact imaging systems, the micro-motion mechanism is selected from a micro-motor, a micro-gear rack mechanism or a micro-linkage mechanism.

[0027] Another aspect of the present invention provides a method for preparing the above-mentioned high fault-tolerant compact imaging system, comprising the following steps: (i) obtaining parameters of a conjugate lens and a main camera lens and selecting the conjugate lens and the main camera lens;

[0028] The parameters are:

[0029] Focus distance u between main lens and conjugate lens a ,u b ;

[0030] The permissible micro-motion range of the conjugate lens is d b ;

[0031] The allowable micro-motion range of the main camera lens is d a ;

[0032] The parameters should meet the longitudinal dimension limit value L 1 And magnification requirements:

[0033] Magnification requirement: Focus distance u of the main camera lens a Focus distance u with conjugate lens b The ratio u a / u b accomplish;

[0034] Longitudinal dimension limit L 1 : The distance u from the imaging plane to the object plane a +u b + conjugate and principal gap L 2 Less than or equal to L 1 ;

[0035] (ii) (ii) arranging an object holder, a conjugate lens with a micro-motion mechanism, a main lens with a micro-motion mechanism, and an imaging surface element along the optical axis according to the parameters;

[0036] (iii) Adjust the image distance so that a clear image is obtained on the imaging plane; or adjust the object distance until the object falls at the focal length of the conjugate lens; the image distance is equal to u a ±1 / 2d a， Object distance is equal to u b ±1 / 2d b ;

[0037] The micro-motion mechanism of the conjugate lens is configured so that the conjugate lens can move within an allowable micro-motion range d b The micro-motion mechanism of the main camera lens is configured to allow the main camera lens to move within an allowable micro-motion range d a The inner optical axis moves so that the object holder (object) can form a clear image on the imaging surface element within the movable range D.

[0038] In a preferred embodiment, a micro-motion mechanism is provided for the object holder so that the object holder can move along the optical axis within the movable range D; the movable range of the object holder satisfies the following conditions:

[0039] It can keep the relative distance between the object and the conjugate lens at object distance u b ±1 / 2d b range, and

[0040]

[0041] Where: u a and u b Respectively represent the focusing distances of the main lens and the conjugate lens;

[0042] The object distance refers to the distance from the object to the optical center of the conjugate lens;

[0043] d b Take the maximum value and substitute it into formula (5) for calculation;

[0044] d a Take the maximum value and substitute it into formula (5) for calculation.

[0045] In the preferred preparation method, step (iii) adjusting the image distance so as to obtain a clear image on the imaging surface; or adjusting the object distance until the photographed object falls at the focal length of the conjugate lens, refers to using the following debugging steps to compensate for the mechanical errors during production at the factory:

[0046] (i) Observe the sample, fix the main camera lens to focus at the center position, fine-tune the conjugate lens until it is in focus, and then fix the adjusted conjugate lens position; when the user observes the actual sample, fine-tune the main camera lens to focus on the sample to obtain a clear image;

[0047] or

[0048] (ii) Observe the sample, fix the conjugate lens to focus at the center position, fine-tune the main camera lens until it is in focus, and then fix the adjusted main camera lens position. When the user observes the actual sample, he only needs to fine-tune the conjugate lens to focus on the sample to obtain a clear image.

[0049] In the preferred preparation method, it also includes using a focusing algorithm to find the best focusing position of the conjugate lens for obtaining the clearest image. After obtaining the position parameters, they are used to adjust the object distance in step iii of the preparation method, i.e., factory debugging, to compensate for mechanical errors during production.

[0050] The focusing algorithm steps are as follows:

[0051] (1) capturing sample images at equally spaced positions within the focusing range of the conjugate lens, and calculating the clarity of the image at each position, wherein the clarity evaluation criterion may be a focusing algorithm, such as but not limited to the Tennengrad and Brenen algorithms;

[0052] (2) Compare the images at each position and use the maximum value search algorithm to determine the position of the clearest image, which is the focus position;

[0053] The maximum value search algorithm is implemented by sequential search and binary search; preferably, a machine learning algorithm is used to accelerate the search process.

[0054] In summary, the highly fault-tolerant compact imaging system provided by the present invention provides an allowable moving range for the conjugate lens by setting a micro-motion mechanism for the conjugate lens and combining an innovative focusing algorithm. The movable range expands the focusing range for forming a clear image. Specifically, according to the formula (u a and u b Represents the focusing distance between the main lens and the conjugate lens, d b d a represents the allowable micro-motion range of the conjugate lens and the main camera lens, and D represents the micro-motion range of the object being photographed). In the prior art, Figure 2 As shown, 1) Since the conjugate lens is usually fixed, that is, d b is zero; 2) the usual u a >u b , based on the formula, u a The contribution of regulation is much smaller than u b Therefore, the movable range of the object is very small, and a clear image cannot be formed outside this range. The accuracy of imaging focus is very high, and under the scale of compact imaging systems (usually the total size along the optical axis is in the range of 10 to 30 mm), the tolerances of internal components themselves or assembly will also have a significant impact on the focus, increasing the accuracy requirements for focusing.

[0055] The design of the present invention provides a micro-motion range for the conjugate lens. Comparative experimental data show that the movable range of the object is greatly expanded, the fault tolerance of the imaging system is improved, and self-calibration can be easily performed by fine-tuning the conjugate lens or the main camera lens to compensate for mechanical errors during production, which greatly reduces the focus accuracy requirements of the compact optical system module during manufacturing, assembly and use.

[0056] The highly fault-tolerant compact imaging system provided by the present invention has a conjugate lens that can be slightly moved. Another major technical advantage brought about by this is that it can support the use of a focusing algorithm to find the best focusing position of the conjugate lens for obtaining the clearest image and an acceptable adjustment space, so that the conjugate lens can be adjusted to the best focusing position during factory debugging to compensate for mechanical errors during production, thereby ensuring the focusing accuracy and imaging quality of the imaging system during use. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 .Shows the parameter relationship and calculation principle between the various components in the present invention.

[0058] Figure 2 .A compact imaging system setup in the prior art, wherein the conjugate lens is fixed.

[0059] Figure 3 An embodiment of the present invention is shown in which both the conjugate lens and the main camera lens are provided with a micro-motion mechanism. DETAILED DESCRIPTION

[0060] The present invention is described below in conjunction with specific implementation schemes, but the following content is only used as an exemplary description of the present invention and is not intended to limit the present invention.

[0061] The following detailed description illustrates certain embodiments of the present invention by way of example and not limitation. The section headings and any subheadings used herein, if any, are for organizational purposes only and should not be construed as limiting the subject matter described in any way. The content under a section heading and / or subheading is not limited to the section heading and / or subheading, but applies to the entire description of the present invention.

[0062] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0063] Optical element settings and parameters in the highly fault-tolerant compact imaging system of the present invention

[0064] Figure 1 The positional relationship of the object, conjugate lens, main camera lens, and imaging surface element arranged along the optical axis in the compact imaging system of the present invention is illustrated, wherein the conjugate lens and the main camera lens are respectively provided with a micro-motion mechanism for fine adjustment along the optical axis. The appropriate object distance and image distance of the compact imaging system are calculated so that when the object is placed within the object placement range (the movable range D of the object) of the system, a clear image can be formed on the imaging surface element.

[0065] Figure 3 A schematic diagram of an embodiment.

[0066] The distance from the object to the optical center of the conjugate lens is the object distance, and the distance from the optical center of the main camera lens to the imaging surface element is the image distance; the object distance and the conjugate lens focusing distance u b The relationship is: object distance equals u b ±1 / 2d b， The image distance and the main camera lens focus distance u a The relationship is: image distance equals u a ±1 / 2d a ;

[0067] The movable range D of the object satisfies the following relationship:

[0068]

[0069] Main camera lens focusing distance u a ,

[0070] Conjugate lens focusing distance u b ,

[0071] Maximum micro-motion range of the main camera lens d a ,

[0072] Maximum value d of the conjugate lens micro-motion range b ;

[0073] The principle of the present invention is based on the above formula, and its derivation process is as follows:

[0074] The maximum movable range D for clear imaging of the object consists of two parts: the maximum value d of the micro-motion range of the conjugate lens b , and the maximum value da of the main camera lens micro-motion range is equivalent to the conjugate lens micro-motion range d′ b , that is, D <= db + d′ b

[0075] Main camera lens micro-motion range d a Equivalent to the conjugate lens fine movement range d′ b It can be obtained by the Gaussian imaging formula. Gaussian imaging formulas (1) and (2) are known, where it is assumed that the micro-motion direction d a and d′ b on the contrary):

[0076]

[0077] Since the micro-motion range d is much smaller than the focal length u, the formula (2) can be Taylor expanded to obtain the formula (3):

[0078] Subtracting formula (1) from formula (3) yields:

[0079] Then transform to: So the movable range D should satisfy:

[0080] In the prior art, since the conjugate lens is usually fixed, that is, d b is 0, and usually u a >u b , based on the formula Main camera lens a The contribution of regulation is much smaller than u b , so the movable range of the object being photographed is very small; however, the design of the present invention provides a micro-motion range for the conjugate lens, which significantly increases the movable range of the object being photographed.

[0081] The following comparative examples and embodiments illustrate the effect of setting a conjugate lens capable of micro-movement on the movable range of the subject:

[0082] Comparative Example 1: The longitudinal dimension limit of the compact imaging system is 10 mm, and the magnification is 2.2 times. Based on this, the selection and setting parameters of the main camera lens and its conjugate lens are as follows, where the conjugate lens is fixed.

[0083] Main camera lens: u a =4.4mm,d a =300μm

[0084] Conjugate lens: u b =2.0mm,d b =0μm, that is, the conjugate lens is fixed.

[0085] The range D within which the subject can move to obtain a clear image is calculated as follows:

[0086]

[0087] Example 1 The longitudinal dimension limit of the compact imaging system is 10 mm, the magnification is 2.2 times, and a micro-motion mechanism is set for the conjugate lens so that it can move 250 μm in the optical axis direction. The setting parameters of the main camera lens and the conjugate lens are as follows: Main camera lens: u a =4.4mm,d a =300μm

[0088] Conjugate lens: u b =2.0mm,d b =250μm

[0089] The range D within which the subject can move to obtain a clear image is calculated as follows:

[0090]

[0091] Example 2 The longitudinal dimension limit of the compact imaging system is 10 mm, and the magnification is 2.2 times. A micro-motion mechanism is set for the conjugate lens in the system so that it can move 250 μm in the optical axis direction. The setting parameters of the main camera lens and the conjugate lens are as follows:

[0092] Main camera lens: U a =4.4mm,d a =500μm

[0093] Conjugate lens: Ub = 2.0 mm, d b =250μm

[0094] The range D within which the subject can move to obtain a clear image is calculated as follows:

[0095]

[0096] Example 3: Compact imaging system with a longitudinal dimension limit of 10 mm and a magnification of 2.2 times. A micro-motion mechanism is provided for the conjugate lens in the system so that it can move 500 μm in the optical axis direction. The setting parameters of the main camera lens and the conjugate lens are as follows:

[0097] Main camera lens: Ua=4.4mm,d a =300μm

[0098] Conjugate lens: Ub = 2.0 mm, d b =500μm

[0099] The range D within which the subject can move to obtain a clear image is calculated as follows:

[0100]

[0101] It can be seen from the above examples that when the micro-motion mechanism is introduced to enable the conjugate lens to move in the direction of the optical axis, the movable range D of the object for obtaining a clear image is significantly expanded. This change can greatly reduce the precision requirements for the focusing operation and can compensate for the influence of the mechanical errors of the components themselves and the mechanical errors caused by assembly during production on the focusing.

[0102] The components in the highly fault-tolerant compact imaging system of the present invention can all be purchased, and are different from the prior art only in the parameter selection of the components, the system structure, the assembly method, and the debugging method. Specifically, the preparation method of the highly fault-tolerant compact imaging system includes the following steps:

[0103] i. Select the conjugate lens and main lens that meet the requirements according to the longitudinal size limit and magnification requirements of the imaging system.

[0104] Parameter u a ,ub , d a , d b ;

[0105] u a ,u b Respectively represent the focusing distances of the main lens and the conjugate lens;

[0106] d b Indicates the allowable micro-motion range of the conjugate lens;

[0107] d a Indicates the allowable micro-motion range of the main camera lens; magnification requirement: through the main camera lens focusing distance u a Focus distance u with conjugate lens b The ratio u a / u b accomplish;

[0108] Longitudinal dimension limit L 1 : The distance u from the imaging plane to the object plane a +u b + conjugate and principal gap L 2 Less than or equal to L 1 ;

[0109] ii. Arranging an object holder, a conjugate lens with a micro-motion mechanism, a main lens with a micro-motion mechanism, and an imaging surface element along the optical axis,

[0110] iii. Adjust the image distance to obtain a clear image on the imaging surface; or adjust the object distance until the object falls at the focal length of the conjugate lens; the image distance is equal to u a ±1 / 2d a， Object distance is equal to u b ±1 / 2d b ;

[0111] The micro-motion mechanism of the conjugate lens is configured so that the conjugate lens can move within an allowable micro-motion range d b The micro-motion mechanism of the main camera lens is configured to allow the main camera lens to move within an allowable micro-motion range d a The inner optical axis moves so that the object holder (object) can form a clear image on the imaging surface element within the movable range D.

[0112] In a preferred embodiment of the preparation method, the method further includes providing a micro-motion mechanism for the object holder so that the object holder can move along the optical axis within the movable range D; the movable range of the object holder satisfies the following conditions:

[0113] It can keep the relative distance between the object and the conjugate lens at object distance u b ±1 / 2db range, and

[0114]

[0115] Where: u a and u b Respectively represent the focusing distances of the main lens and the conjugate lens;

[0116] The object distance refers to the distance from the object to the optical center of the conjugate lens;

[0117] d b Take the maximum value and substitute it into formula (5) for calculation;

[0118] d a Take the maximum value and substitute it into formula (5) for calculation.

[0119] In the preferred preparation method, step iii of adjusting the image distance so that a clear image is obtained on the imaging surface; or adjusting the object distance until the photographed object falls at the focal length of the conjugate lens, refers to using the following debugging steps at the factory to compensate for the mechanical errors during production:

[0120] (i) Observe the sample, fix the main camera lens to focus at the center position, fine-tune the conjugate lens until it is in focus, and then fix the adjusted conjugate lens position; when the user observes the actual sample, fine-tune the main camera lens to focus on the sample to obtain a clear image;

[0121] or

[0122] (ii) Observe the sample, fix the conjugate lens to focus at the center position, fine-tune the main camera lens until it is in focus, and then fix the adjusted main camera lens position. When the user observes the actual sample, he only needs to fine-tune the conjugate lens to focus on the sample to obtain a clear image.

[0123] In the present invention, according to the requirements of the imaging system for the actual application scenario or sequencing needs, the components and parameters in the system are configured in the following steps:

[0124] (1) Select the main camera lens and determine the focal distance u of the main camera lens a And its own micro-motion range d a :

[0125] Determine the main camera lens focal distance u according to the following conditions a Focus distance u with conjugate lens b ;

[0126] Required magnification: Focus distance u through the main camera lens a Focus distance u with conjugate lens b The ratio is achieved;

[0127] Longitudinal dimension limit L1 : The distance u from the imaging plane to the object plane a +u b + conjugate and principal gap L 2 Less than or equal to L 1 ;

[0128] (2) Based on the determined main camera lens focal distance u a Select the main camera lens, the main camera lens has a built-in micro-motion range value d a ;

[0129] (3) Preliminarily determine the movable range D required for the object according to the test requirements; for example, in some applications, it is necessary to scan the object, and the up and down range of the object under the lens is the actually required movable range D.

[0130] (4) u obtained according to steps (1) to (3) a， u b , d a， D and formula Determine the fine motion range d of the conjugate lens b The minimum value of u is selected accordingly. b , d b Conditions, and meet the longitudinal dimension limit value L 1， A conjugate lens with a magnification ratio and a movable range D of the subject.

[0131] Similarly, in some application scenarios, when the u of the main camera and the conjugate lens a， u b , d a， d b If the parameters are determined or given in advance, the formula Calculate the maximum range of the movable range D of the object, and then determine the application scenario for the system adaptation, or adjust the parameter d of the conjugate lens according to the feasibility of subsequent manufacturing and engineering cost. b Make adjustments to optimize product design.

[0132] The highly fault-tolerant compact imaging system provided by the present invention has a conjugate lens that is slightly movable, which brings another major technical advantage in that it can support the focusing algorithm to find the best focusing position of the conjugate lens for obtaining the clearest image. After the position parameters are obtained, they are used to adjust the object distance in step iii of the preparation method, i.e., factory debugging, to compensate for mechanical errors during production.

[0133] The present invention adopts a focusing algorithm to determine the optimal focusing position of the conjugate lens

[0134] (1) Shooting sample images at equally spaced positions within the focus range, and calculating the clarity of the image at each position, wherein the clarity evaluation criterion may adopt a focusing algorithm such as, but not limited to, the Tennengrad and Brenen algorithms;

[0135] (2) Compare the images at each position, and the clearest image position is the focus position;

[0136] Generally, within the focus range, the relationship between clarity and shooting focus position follows a single-peak curve (the specific value is affected by the field of view content). Therefore, the focus position is achieved using the maximum value search algorithm.

[0137] During the maximum value search process, the next search position and direction can be estimated based on the image clarity values ​​of the positions that have been searched, and then the moving direction and distance of the next one or several positions can be determined.

[0138] The maximum value search algorithm is implemented by sequential search and binary search; preferably, a machine learning algorithm is used to accelerate the search process.

[0139] Existing imaging systems can only search and compare the best imaging position within a very limited range, and cannot support the implementation of the focusing algorithm, so it is usually difficult to achieve the optimal solution. However, after the present invention introduces the conjugate lens micro-motion range db, the new imaging system physically supports the feasibility and effectiveness of the focusing algorithm, that is, it provides greater adjustability to achieve the optimal solution, thereby optimizing the imaging quality.

Claims

1. A highly fault-tolerant compact imaging system, comprising: A conjugate lens, a main lens, and an imaging surface element are arranged in sequence along the optical axis from the object side; It also includes micro-motion mechanisms respectively configured for the conjugate lens and the main camera lens; The micro-motion mechanism of the conjugate lens is configured so that the conjugate lens can move along the optical axis within a micro-motion range d b , and the micro-motion mechanism of the main camera lens is configured so that the main camera lens can move along the optical axis within a micro-motion range d a , so that the photographed object can still form a clear image on the imaging surface element within the movable range D.

2. The highly fault-tolerant compact imaging system according to claim 1, further comprising a photographic object holder, the photographic object holder being movable along the optical axis so as to adjust the movement of the photographic object within the movable range D; The movable range D of the object holder satisfies the following conditions: Keep the relative distance between the object and the conjugate lens at object distance u b ±1 / 2d b range, and in: u a and u b Respectively represent the focusing distances of the main lens and the conjugate lens; The object distance refers to the distance from the object to the optical center of the conjugate lens, and the range is u b ±1 / 2d b ; d b Take the maximum value and substitute it into formula (5) for calculation; d a Take the maximum value and substitute it into formula (5) for calculation.

3. According to the highly fault-tolerant compact imaging system of claim 1, the setting position of the object holder satisfies the following conditions: the total distance from the object, the conjugate lens, the main camera lens to the imaging surface element, that is, the longitudinal dimension of the compact imaging system is less than 30.0 mm.

4. The highly fault-tolerant compact imaging system according to claim 3, wherein the longitudinal dimension is 5 mm. 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, 22mm, 25mm, or a range between any two of the longitudinal dimension values.

5. The highly fault-tolerant compact imaging system according to claim 1, wherein the allowable micro-motion range d of the conjugate lens is b The allowable micro-motion range d of the main camera lens is 10 to 600 microns, 10 to 500 microns, 10 to 400 microns, 10 to 300 microns, 10 to 200 microns or 10 to 100 microns. a It is 10-800 microns, 10-700 microns, 10-600 microns, 10-500 microns, 10-400 microns, 10-300 microns, 10-200 microns or 10-100.

6. According to the high fault-tolerant compact imaging system of claim 3, the distance from the optical center of the main camera lens to the imaging surface, i.e., the image distance, is in the range of u a ±1 / 2d a ; The object distance is between 0.2 and 10.0 mm, and the image distance is between 0.2 and 10.0 mm; The object distance is between 0.2 and 5.0 mm, and the image distance is between 0.2 and 5.0 mm.

7. The highly fault-tolerant compact imaging system according to any one of claims 1 to 6, characterized in that: The magnification of the compact imaging system is the focal length u of the main camera lens. a The focal distance u from the conjugate lens b The ratio Ua / Ub is 0.5~50.

8. The highly fault-tolerant compact imaging system according to any one of claims 1 to 6, wherein the imaging surface element is a CCD sensor or a CMOS sensor.

9. According to any one of claims 1 to 6, the high fault-tolerant compact imaging system, the micro-motion mechanism is selected from a micro-motor, a micro-gear rack mechanism or a micro-connecting rod mechanism.

10. The method for preparing the highly fault-tolerant compact imaging system according to any one of claims 1 to 9, comprising the following steps: (i) obtaining parameters of a conjugate lens and a main lens and selecting the conjugate lens and the main lens; The parameters are: Focus distance u between main lens and conjugate lens a ,u b ; The permissible fine motion range of the conjugate lens is d b ; The allowable micro-motion range of the main camera lens is d a ; The parameters should meet the longitudinal size limit L1 and magnification requirements of the imaging system: Magnification requirement: Focus distance u of the main camera lens a Focus distance u with conjugate lens b The ratio u a / u b accomplish; Longitudinal size limit L1: distance u from the imaging plane to the object plane a +u b + The conjugate and principal gap L2 is less than or equal to L1 (ii) arranging an object holder, a conjugate lens with a micro-motion mechanism, a main lens with a micro-motion mechanism, and an imaging surface element along the optical axis according to the parameters, (iii) Adjust the image distance so that a clear image is obtained on the imaging plane; or adjust the object distance until the object falls at the focal length of the conjugate lens; the image distance is equal to u a ±1 / 2d a， Object distance is equal to u b ±1 / 2d b ; The micro-motion mechanism of the conjugate lens is configured so that the conjugate lens can move within an allowable micro-motion range d b The micro-motion mechanism of the main camera lens is configured to allow the main camera lens to move within an allowable micro-motion range d a The inner optical axis moves so that the object holder (object) can form a clear image on the imaging surface element within the movable range D.

11. The preparation method according to claim 10, further comprising providing a micro-motion mechanism for the object holder, so that the object holder can move along the optical axis within the movable range D; the movable range of the object holder satisfies the following conditions: It can keep the relative distance between the object and the conjugate lens at object distance u b ±1 / 2d b range, and in: u a and u b Respectively represent the focusing distances of the main lens and the conjugate lens; The object distance refers to the distance from the object to the optical center of the conjugate lens; d b Take the maximum value and substitute it into formula (5) for calculation; d a Take the maximum value and substitute it into formula (5) for calculation.

12. The preparation method according to claim 10, wherein step (iii) adjusting the image distance so as to obtain a clear image on the imaging surface; or adjusting the object distance until the photographed object falls at the focal length of the conjugate lens, refers to using the following debugging steps to compensate for mechanical errors during production at the factory: (i) Observe the sample, fix the main camera lens to focus at the center position, fine-tune the conjugate lens until it is in focus, and then fix the adjusted conjugate lens position; when the user observes the actual sample, fine-tune the main camera lens to focus on the sample to obtain a clear image; or (ii) Observe the sample, fix the conjugate lens to focus at the center position, fine-tune the main camera lens until it is in focus, and then fix the adjusted main camera lens position. When the user observes the actual sample, he only needs to fine-tune the conjugate lens to focus on the sample to obtain a clear image.

13. The preparation method according to any one of claims 10 to 12 further comprises using a focusing algorithm to find the best focusing position of the conjugate lens for obtaining the clearest image, and after obtaining the position parameter, it is used to adjust the object distance in step iii of the preparation method, i.e., factory debugging, to compensate for mechanical errors during production.

14. The preparation method according to claim 13, wherein the steps of the focusing algorithm are as follows: (1) capturing sample images at equally spaced positions within the focusing range of the conjugate lens, and calculating the clarity of the image at each position, wherein the clarity evaluation criterion may be a focusing algorithm, such as but not limited to the Tennengrad and Brenen algorithms; (2) Compare the images at each position and use the maximum value search algorithm to determine the position of the clearest image, which is the focus position.

15. The preparation method according to claim 14, wherein the maximum value search algorithm is implemented by sequential search or binary search; preferably, the search process is accelerated by a machine learning algorithm.

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