CN114280769B - High-sensitivity optical imaging system, method and device - Google Patents

Abstract

The present invention relates to a high sensitivity optical imaging system, method and apparatus. A high-sensitivity optical imaging system comprises a light source, a half mirror, a lens assembly, a sensing chip and a controller; the lens assembly includes one or more optical lenses arranged along a coaxial line; the half mirror is arranged at the rear position of the optical lens nearest to the object to be measured; the light source is arranged above the reflecting surface of the half reflecting mirror, which faces the direction of the object to be detected; and the controller is used for imaging the surface of the object to be detected by driving one or more of all the moving mechanisms to perform micro-movement and combining the light source and the sensing chip with a gradient measurement algorithm or a contrast measurement algorithm. Based on micro-movement of related imaging elements and matching with a gradient measurement algorithm or a contrast measurement algorithm, the sensitivity for optical imaging is improved, the cost is not obviously increased, the method is convenient and quick, and the application field is wide.

Description

High-sensitivity optical imaging system, method and device

Technical Field

The present invention relates to the field of optical imaging, and in particular, to a high sensitivity optical imaging system, method and apparatus.

Background

The sensitivity of the imaging device is generally greatly affected by sensor noise. There are two types of image sensors currently in common, CMOS (complementary metal oxide semiconductor) type, which are relatively inexpensive and common but have low sensitivity, and CCD (charge coupled device) type, which are relatively high in sensitivity and cost, which are commonly used in higher end applications. Taking the CCD type as an example, its sensitivity is typically limited by shot noise, dark current noise, and read circuit noise. To increase imaging sensitivity, one approach in the industry is to control the temperature of the sensor chip well below room temperature, but this greatly increases the cost and applicability of the device and has limited cooling and noise reduction ranges.

Another method of improving sensitivity, commonly known in the industry, has been to modify the optical design of imaging systems, known as DIFFERENTIALINTERFERENCE CONTRAST (differential interference contrast, DIC) technology. DIC-based microscopes are also commonly named by the inventors of DIC and are known as Nomarski microscopes. DIC technology illuminates two adjacent reflection points on the surface of an object by dividing each illumination beam into two adjacent beams by special optical elements added to the illumination path. In the imaging light path, the reflected light of the two adjacent points is combined into one pixel of the image plane, and the light intensity of the pixel is proportional to the light field difference of the two adjacent reflected points. The DIC technology can greatly improve imaging sensitivity of a certain type of reflector, and thus has many applications in related fields, particularly biomedical fields. But DIC techniques must rely on non-uniformity of the optical phase of the object to increase sensitivity. DIC techniques offer little advantage over conventional microscopy for many other applications, such as inspection of silicon wafer surfaces or optically precise component surfaces.

Patent document CN200910076054.5 discloses an optical coherence tomography skin diagnostic device for real-time imaging, which belongs to the field of optical imaging devices. The apparatus includes: the system comprises a power supply, a light source control circuit, a light source, an indication light source, a first optical fiber coupler, a second optical fiber coupler, an OCT probe, an optical delay, a photoelectric detector, a signal processing and control circuit and a calculation processing and display device. The imaging equipment takes an optical coherence imaging technology (OCT probe) as a core, rapidly processes signals through a signal processing and control circuit, and is matched with a calculation processing display device, so that the imaging speed and the resolution of images are improved; the design of the broadband light source and the duckbill probe suitable for skin scanning makes the device suitable for scanning human skin. But the problems in the foregoing are not effectively solved, i.e., there is not much benefit in terms of sensitivity of the imaging device.

Thus, the existing imaging device sensitivity technology has defects and needs to be improved and improved.

Disclosure of Invention

In view of the foregoing deficiencies of the prior art, it is therefore an object of the present invention to provide a high sensitivity optical imaging system, method and apparatus for solving the problem of low imaging sensitivity of the imaging device in the prior art.

In order to achieve the above purpose, the invention adopts the following technical scheme:

a high-sensitivity optical imaging system comprises a light source, a half mirror, a lens assembly, a sensing chip and a controller; the lens assembly includes one or more optical lenses arranged along a coaxial line; the half mirror is arranged at the rear position of the optical lens nearest to the object to be measured; the light source is arranged above the reflecting surface of the half reflecting mirror, which faces the direction of the object to be detected;

One or more of each optical lens and the sensing chip is/are provided with a moving mechanism, and all the moving mechanisms are connected with the controller; the sensing chip and the light source are respectively connected with the controller;

And the controller is used for imaging the surface of the object to be detected by driving one or more of all the moving mechanisms to perform micro-movement and combining the light source and the sensing chip with a gradient measurement algorithm or a contrast measurement algorithm.

In the preferred high-sensitivity optical imaging system, the half mirror body forms a predetermined angle with the axis.

Preferably, the optical lens is a single lens or a compound lens.

Preferably, the high-sensitivity optical imaging system, the moving mechanism can drive the corresponding element to move longitudinally or transversely

Preferably, the high-sensitivity optical imaging system further comprises an objective table, wherein the objective table is used for carrying an object to be detected and is provided with a corresponding moving mechanism, and the moving mechanism is connected with the controller and performs micro-movement according to the instruction of the controller.

Preferably, the high-sensitivity optical imaging system, the moving mechanism comprises a PZT mover, a MEMS mover and a voice coil motor.

Preferably, in the high-sensitivity optical imaging system, the gradient measurement algorithm includes the steps of:

Adjusting each imaging element in the imaging system to obtain a first image function P1 (x, y);

Adjusting one or more imaging elements in the imaging system to perform micro-movements in a lateral or longitudinal direction to obtain a second image function P2 (x, y);

a gradient function Q (x, y) =p2 (x, y) -P1 (x, y) is obtained.

Preferably, the high-sensitivity optical imaging system, the specific steps of the contrast measurement algorithm include:

Adjusting each imaging element in the imaging system to obtain a first image function T1 (x, y);

micro-movement is carried out on an adjustable imaging element in the adjusting imaging system in the longitudinal positive and negative direction and the transverse positive and negative direction respectively, and a second image function T2 (x, y), a third image function T3 (x, y), a fourth image function T4 (x, y) and a fifth image function T5 (x, y) are obtained respectively;

The contrast function C (x, y) =t2 (x, y) +t3 (x, y) +t4 (x, y) +t5 (x, y) -4×t1 (x, y) is obtained.

A method of high sensitivity optical imaging using said imaging system, comprising the steps of:

adjusting each imaging element in the imaging system to obtain a first image function;

The sensitivity of the imaging system is improved using a gradient measurement algorithm or a contrast measurement algorithm.

An optical imaging device uses the imaging system to acquire images of objects to be detected by using the imaging method.

Compared with the prior art, the high-sensitivity optical imaging system, the method and the device provided by the invention have the following beneficial effects:

The high-sensitivity optical imaging system provided by the invention realizes the improvement of sensitivity for optical imaging based on micro-movement of related imaging elements and matching with a gradient measurement algorithm or a contrast measurement algorithm, has the advantages of unobvious cost increase, convenience and rapidness, and wide application field, and has great progress.

Drawings

FIG. 1 is a block diagram of an imaging system provided by the present invention;

FIG. 2 is a flow chart of a gradient measurement algorithm provided by the present invention;

FIG. 3 is a flow chart of a contrast measurement algorithm provided by the present invention;

fig. 4 is a schematic diagram illustrating movement of individual imaging elements in an imaging system according to the present invention.

Detailed Description

In order to make the objects, technical solutions and effects of the present invention clearer and more specific, the present invention will be described in further detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.

Those of ordinary skill in the art will realize that the foregoing general description and the following detailed description are illustrative of specific embodiments of the present invention and are not intended to be limiting.

The terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps, but may include other steps not expressly listed or inherent to such process or method. Likewise, without further limitations, one or more devices or subsystems beginning with "comprising". A "neither does an element or structure or component have no further limitations, excluding the presence of other devices or other subsystems or other elements or other structures or other components or other devices or other subsystems or other elements or other structures or other components. The appearances of the phrases "in one embodiment," "in another embodiment," and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

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.

Referring to fig. 1, the present invention provides a high-sensitivity optical imaging system 100, which includes a light source 10, a half mirror 11, a lens assembly, a sensor chip 19, and a controller (not shown); the lens assembly includes one or more optical lenses (in this embodiment, a first convex lens 12 and a second convex lens 14) arranged along a coaxial line; the half mirror 11 is installed at a rear position of an optical lens (in the present embodiment, installed at the rear of the first convex lens 12) nearest to the object to be measured; the light source 10 is arranged above the reflecting surface of the half reflecting mirror 11 opposite to the direction of the object to be detected; further, the light source 10 is driven to be turned on and off by the controller by using a light source device commonly used in the art, and the controller can turn on the light source 10 when the image is required to be acquired according to the requirement, and turn off the light source 10 when the image is not acquired. The half mirror 11 body forms a preset angle with the axis; the half mirror 11 is not particularly limited as long as it can reflect the light of the light source 10 to the surface of the object under the predetermined angle, using a half mirror 11 commonly used in the art; the predetermined angle is preferably 15 ° to 60 °, further preferably 45 °. The basic parameters of the first convex lens 12 and the second convex lens 14 are generally set by using imaging lenses in the field, and are not particularly limited; the basic parameters comprise a field angle, a focal length, materials and the like, and the basic parameters are set according to the requirement of acquiring the image, so that the invention is not limited; specifically, in this embodiment, the first convex lens 12 is an objective lens, and the second convex lens 14 is a focusing lens. The sensor chip 19 is preferably a CCD (charge coupled DEVICE CAMERA) or CMOS (Complementary Metal-Oxide-Semiconductor) image sensor. The controller is preferably an MCU (Micro controller Unit, micro control unit), and the specific model is not limited. It should be noted that, the mounting distances among the first convex lens 12, the half mirror 11, the second convex lens 14, and the sensor chip 19 may be adaptively set according to the focal lengths of the first convex lens 12 and the second convex lens 14, and a distance design commonly used in the art may be used, which is not limited by the present invention.

One or more of each of the optical lenses and the sensor chip 19 is provided with a moving mechanism, and all moving mechanisms are connected with the controller; the sensor chip 19 and the light source 10 are respectively connected with the controller; that is, in the present embodiment, one or more of the first convex lens 12, the second convex lens 14, and the sensor chip 19 are provided with moving mechanisms, and all the moving mechanisms are connected to the controller; the sensor chip 19 and the light source 10 are respectively connected with the controller; further, the moving mechanism is mainly used for driving the corresponding imaging element to perform position adjustment and micro-movement, and the position adjustment is specifically a process of detecting and focusing an object to be detected; the movement amplitude of the micro-movements is usually small, and is generally between 0.1 and 10 times the pixel size of the sensor chip 19 per movement amplitude unit.

The controller performs micro-movement by driving one or more of all the moving mechanisms, and images the surface of the object 18 to be detected in combination with the light source 10 and the sensor chip 19 in combination with a gradient measurement algorithm or a contrast measurement algorithm.

Specifically, the imaging system 100 provided by the present invention operates according to the following principles: the controller is used for controlling the relative positions of the first convex lens 12, the second convex lens 14 and the sensing chip 19, and controlling the relative positions of the first convex lens 12 and the object to be detected at the same time, so that imaging is clear, during adjustment, the light source 10 can be always opened to be matched with dynamic adjustment, can also be opened at each fixed position to check whether the light source is adjusted to a proper position, after the position is adjusted, the controller drives one or more (independently adjusts one imaging element when driving one, drives a plurality of imaging elements to be linked, and the operation principle of two working states is the same and is not repeated), the moving mechanism performs micro-movement, preferably performs movement of one movement range unit every micro-movement, and of course, the movement of a plurality of movement range units can also be performed, the distance of each movement is not limited, and the type of the corresponding object to be detected is not limited; after each micro-movement is executed, a surface image of the object to be detected is acquired, and then the gradient measurement algorithm or the contrast measurement algorithm is used for improving the sensitivity of the surface of the object to be detected, so that the method is convenient and quick, the steps are simple, the system architecture is relatively simple, and the sensitivity of the imaging system 100 can be greatly improved without improving the cost.

Correspondingly, the invention also provides a high-sensitivity optical imaging method, which uses the imaging system 100, and comprises the following steps:

Adjusting each imaging element in the imaging system 100 to obtain a first imaging function; specifically, the image function is obtained by converting an optical image of the sensing surface of the sensor chip 19 into an image signal, which is a common technique in the art.

The sensitivity of the imaging system 100 is improved using a gradient measurement algorithm or a contrast measurement algorithm.

Specifically, in this embodiment, the specific operation principle of the imaging method is as follows: the light source 10 generates illumination light 16, which is incident on the half mirror 11. The half mirror 11 is a common optical element that reflects nearly half of incident light and transmits the other half. The half mirror 11 propagates a part of the energy reflection of the illumination light 16 (shown in broken lines in the figure) to the left, passes through a first convex lens 12 (commonly referred to as an objective lens), and irradiates an object plane 13. The object plane 13 generally coincides with the surface of the object 18, and the object of the object plane 13 reflects the illumination light 16, producing imaging light 17. After passing through the first convex lens 12, a part of the imaging light 17 passes through the half mirror 11, passes through the second convex lens 14, and finally forms an image of the object plane 13 at the image plane 15. The image plane 15 coincides with the sensing surface of the sensor chip 19, the position of any point in the object plane 13 is marked by (X, Y) coordinates, and the position of any point in the image plane 15 is marked by (X, Y) coordinates. The sensor chip 19 may be a CCD or CMOS image sensor which converts an optical image on its sensing surface into an image signal and outputs the data to a computer or a separate image processor through a reading circuit.

The specific formula of the image function is as follows:

P(x,y,t)＝A(a+x/m,b+y/m)*f(x,y)+n(x,y,t)；

Wherein P (X, Y, t) is an image signal (abbreviated as an image function) output by the imaging device, a (X, Y) is a distribution function (abbreviated as an object function) of light intensity of the object plane along with the position (X, Y) of the object plane, f (X, Y) is a spatial modulation function of the imaging device, n (X, Y, t) is a random noise function of the imaging device, where t refers to time because random noise varies with time.

The object-image relationship of the imaging device can be simplified into a one-to-one correspondence between the object plane and each point of the image plane. If the object plane position (X, Y) is imaged at the image plane position (X, Y), the corresponding relationship is: x=a+x/m, y=b+y/m, where (a, b) is an object plane point coordinate corresponding to an image plane origin (0, 0), and m represents an optical magnification of the imaging device. Corresponding to the device shown in fig. 1, the absolute value of the optical magnification m is equal to the focal length ratio of the lenses 14 and 12, and m is actually a negative number because of the inverted relationship of the image to the object. In a typical application, the absolute value of the magnification is greater than 1, i.e. the focal length of lens 14 is greater than the focal length of lens 12. For brevity, we only discuss the case where m=1, i.e., the optical magnification of the imaging device is 1, in the following example. This specialization treatment does not affect the universality of the following analytical conclusions regarding the sensitivity and the applicability of the method according to the invention. It is apparent that when the optical magnification m is 1, the formula of the image function is:

P(x,y,t)＝A(a+x,b+y)*f(x,y)+n(x,y,t)；

When the object function is fixed, the temporal variation of the image function is mainly due to the random noise function n (x, y, t) of the imaging device. Random noise, which is typically dominated by shot noise and dark current noise of the sense die 19, varies randomly over time, may be attenuated by multiple sample averages, or may be reduced by cryogenic means. The spatial modulation function f (x, y) of the imaging device is partially fixed relative to each other, due to differences in the light sensitivity of the different pixels of the sensor chip 19 and differences in the reading of the different pixels by the reading circuit. However, a serious problem is that the f (x, y) function, which is partly due to crosstalk between different pixels, has a certain correlation with the object function itself, and therefore cannot be calibrated out as a completely fixed systematic deviation. As previously mentioned, the sensitivity of the imaging system 100 refers to the ability of us to discern a weak change in the object function a (x, y) with position from the image function P (x, y, t). The weak changes referred to herein may be defined in many ways, but common examples are the following two categories:

Gradient: q (x, y) =a (x+1, y) -a (x, y); a special case of the expression is gradient along the x direction, and in practical application, the gradient function Q (x, y) sometimes represents gradient along other directions (such as the y direction or a direction forming an included angle with the x axis);

contrast ratio: c (x, y) =a (x+1, y) +a (x-1, y) +a (x, y+1) +a (x, y-1) -4*A (x, y); this formula represents the integrated contrast analysis in four directions.

From two weak change formulas of gradient and contrast, it can be clearly known that if the gradient and contrast are directly calculated by using the image function P (x, y, t), the change of the spatial modulation function f (x, y) is multiplied by the change of the object function, which results in indistinguishable sources of change, so that the sensitivity of we perceiving the change of the object function is severely limited by the spatial modulation function. In order to improve imaging sensitivity, in particular, the present invention circumvents the negative effects of the spatial modulation function f (x, y) by providing the gradient measurement algorithm and the contrast measurement algorithm.

In a preferred embodiment, the optical lens is a single lens or a compound lens. The corresponding basic parameters are not limited, and in this embodiment, the focal length of the first convex lens 12 is smaller than the focal length of the second convex lens 14, and further, the focal length of the second convex lens 14 is 2-100 times that of the first convex lens 12. The moving mechanism can drive the corresponding element to move longitudinally (Y direction in figure 1) or transversely (X direction in figure 1) and not in the axial line direction. The device also comprises an objective table for bearing the object 18 to be measured, and a corresponding moving mechanism is configured, wherein the moving mechanism is connected with the controller and performs micro-movement according to the instruction of the controller. That is, the moving mechanism of the first convex lens 12, the second convex lens 14, the stage and the sensor chip 19 may drive the corresponding elements to move longitudinally or transversely. The moving mechanism comprises a PZT (piezoelectric actuator, piezoelectric driver) mover, a MEMS (Micro-electromechanical Systems, micro electro mechanical system) mover and a voice coil motor, which are all commonly used for Micro-movement.

Referring to fig. 2, in this embodiment, the gradient measurement algorithm includes the following steps:

adjusting each imaging element in the imaging system 100 to obtain a first imaging function P1 (x, y);

adjusting one or more imaging elements in the imaging system 100 to perform micro-movements in a lateral or longitudinal direction to obtain a second image function P2 (x, y);

a gradient function Q (x, y) =p2 (x, y) -P1 (x, y) is obtained.

Referring to fig. 3, in this embodiment, the specific steps of the contrast measurement algorithm include:

adjusting each imaging element in the imaging system 100 to obtain a first imaging function T1 (x, y);

The method comprises the steps that an adjustable imaging element in the adjusting imaging system 100 performs micro-movement in a longitudinal positive direction and a transverse positive direction respectively, and a second image function T2 (x, y), a third image function T3 (x, y), a fourth image function T4 (x, y) and a fifth image function T5 (x, y) are acquired respectively;

The contrast function C (x, y) =t2 (x, y) +t3 (x, y) +t4 (x, y) +t5 (x, y) -4×t1 (x, y) is obtained.

Referring specifically to fig. 4, a process of implementing the gradient measurement algorithm and the method for specifically improving imaging sensitivity of the contrast measurement algorithm according to the present invention is illustrated, and for brevity, an illumination light source portion is omitted in the figure, and only an imaging light path is illustrated, compared with several different but equivalent modifications of the imaging system 100 apparatus of fig. 1. Fig. 4 (a) demonstrates the addition of lateral (i.e., X-direction, non-coaxial axis direction in fig. 4) micro-movement to the second convex lens 14, indicated by the double-headed arrow labeled lens 14. Such micro-movement capability may be achieved by various known methods of mounting the lens 14 on a PZT (piezoelectric ceramic) displacer, or on a MEMS (micro-electromechanical) displacer, or on a voice coil motor. The amplitude of the micro-movement is typically small, preferably 0.1 to 10 times the pixel size of the sensor chip 19. Similarly, fig. 4 (b) demonstrates adding lateral micro-motion to the sense die 19, while fig. 4 (c) demonstrates adding lateral micro-motion to the imaged object 18 (or equivalently, to the stage).

Taking the x-direction (i.e., lateral) gradient measurement algorithm as an example, a brief description of how the present invention may be implemented by the imaging system 100 apparatus, uses the gradient measurement algorithm and the contrast measurement algorithm to enhance imaging sensitivity. After the imaging device is adjusted, a first image function obtained by sampling for the first time is as follows:

P1(x,y)＝A(a+x,b+y)*f(x,y)+n1(x,y)；

Where n1 (x, y) is a random noise function obtained from the first image function. Taking the design of fig. 4 (a) as an example, after the second convex lens 14 is moved by an amplitude unit distance along the-x direction, the imaging position of the object plane point (a+x, b+y) on the image plane is changed from the original (x, y) to (x-1, y), so the second image function obtained by the second sampling is:

P2(x,y)＝A(a+x+1,b+y)*f(x,y)+n2(x,y)；

Where n2 (x, y) is a random noise function obtained from the second image function. Note that in the second image function, the spatial modulation multiplier of P2 (x, y) is still f (x, y) because it is largely determined by the characteristics of the sense die 19 and the read circuit, and is largely unaffected by small translations of the object function. Our practical testing of several CMOS and CCD image sensors on the market also demonstrates this. From the integration of the gradient function, it can be seen that:

Q(x,y)＝P2(x,y)-P1(x,y)＝(A(a+x+1,b+y)-A(a+x,b+y))*f(x,y)+n2(x,y)-n1(x,y)

Wherein A (a+x+1, b+y) -A (a+x, b+y) is the x-direction gradient of the objective function at point (a, b). It can be seen from the gradient function Q (x, y) that by measuring and calculating P2-P1, the effect of small variations in the spatial modulation function f (x, y) on the sensitivity has been greatly reduced. Since P2-P1 is directly related to the gradient signal of the object plane, and f (x, y) is just one multiplier factor (also commonly referred to as a gain factor) of the gradient signal. In addition, the random noise term n2-n1 in the gradient function Q (x, y) can be subtracted by cryogenic means or multiple sampling averaging methods known in the art. Other types, such as high sensitivity measurement of y-gradients or contrast, are similar to the basic principles described above and will not be described in detail here.

It should be noted that the sensitivity enhancement principle of the contrast measurement algorithm is the same as that of the gradient measurement algorithm, and will not be described in detail, and those skilled in the art can reasonably infer based on the foregoing.

The present invention also provides an optical imaging device, which uses the imaging system 100 to perform image acquisition on the object 18 to be detected by using the imaging method. Based on the working principle of the imaging system 100 in the foregoing description and using the imaging method provided in the foregoing description, it is a great advance in the art to further improve the imaging sensitivity of the optical imaging device without increasing the cost.

It will be understood that equivalents and modifications will occur to those skilled in the art in light of the present invention and their spirit, and all such modifications and substitutions are intended to be included within the scope of the present invention as defined in the following claims.

Claims (8)

1. The high-sensitivity optical imaging system is characterized by comprising a light source, a half mirror, a lens assembly, a sensing chip and a controller; the lens assembly includes one or more optical lenses arranged along a coaxial line; the half mirror is arranged at the rear position of the optical lens nearest to the object to be measured; the light source is arranged above the reflecting surface of the half reflecting mirror, which faces the direction of the object to be detected;

One or more of each optical lens and the sensing chip is/are provided with a moving mechanism, all the moving mechanisms are connected with the controller, and the moving mechanisms are used for driving the corresponding imaging elements to carry out position adjustment and micro-movement; the sensing chip and the light source are respectively connected with the controller;

The controller is used for driving one or more of the moving mechanisms to perform micro-movement, acquiring a surface image of the object to be detected after each micro-movement is performed, and imaging the surface of the object to be detected by combining the light source and the sensing chip with a gradient measurement algorithm or a contrast measurement algorithm; the gradient measurement algorithm and the contrast measurement algorithm improve imaging sensitivity by avoiding the negative influence of a spatial modulation function;

The gradient measurement algorithm comprises the following steps:

Adjusting each imaging element in the imaging system to obtain a first image function P1 (x, y);

Adjusting one or more imaging elements in the imaging system to perform micro-movements in a lateral or longitudinal direction to obtain a second image function P2 (x, y);

Obtaining a gradient function Q (x, y) =p2 (x, y) -P1 (x, y);

the specific steps of the contrast measurement algorithm comprise:

Adjusting each imaging element in the imaging system to obtain a first image function T1 (x, y);

micro-movement is carried out on an adjustable imaging element in the adjusting imaging system in the longitudinal positive and negative direction and the transverse positive and negative direction respectively, and a second image function T2 (x, y), a third image function T3 (x, y), a fourth image function T4 (x, y) and a fifth image function T5 (x, y) are obtained respectively;

The contrast function C (x, y) =t2 (x, y) +t3 (x, y) +t4 (x, y) +t5 (x, y) -4×t1 (x, y) is obtained.

2. The high-sensitivity optical imaging system according to claim 1, wherein the half mirror body makes a predetermined angle with an axis.

3. The high sensitivity optical imaging system according to claim 1, wherein the optical lens is a single mirror or a compound lens.

4. The high sensitivity optical imaging system according to claim 1, wherein said moving mechanism can move the corresponding element longitudinally or laterally.

5. The high-sensitivity optical imaging system according to claim 1, further comprising a stage for carrying an object to be measured, wherein a corresponding moving mechanism is provided, and wherein the moving mechanism is connected to the controller and performs micro-movement according to an instruction of the controller.

6. The high sensitivity optical imaging system of claim 1, wherein said moving mechanism comprises a PZT mover, a MEMS mover, a voice coil motor.

7. A method of high sensitivity optical imaging, characterized in that the imaging system according to any one of claims 1-6 is used, comprising the steps of:

adjusting each imaging element in the imaging system to obtain a first image function;

The sensitivity of the imaging system is improved using a gradient measurement algorithm or a contrast measurement algorithm.

8. An optical imaging apparatus, wherein the imaging system according to any one of claims 1 to 6 is used for image acquisition of an object to be measured using the imaging method according to claim 7.