阅读说明：本技术 一种基于棱镜分光的水下微光彩色成像设计方法 (Underwater low-light-level color imaging design method based on prism light splitting ) 是由 姜洋 邢妍 李大勇 于 2021-06-23 设计创作，主要内容包括：本发明涉及一种基于棱镜分光的全海深微光彩色成像设计方法,该方法如下：首先分析水下像差的产生原因,确定光学窗口的形状及材料,采用光学性能和抗压性能优异的钢化高硼硅玻璃同心等厚球罩制作光学窗口以保证能量利用效率；根据光学窗口的参数设计校正镜组和成像镜组完成长后工作距的水下专用光学系统设计；计算并控制光线在棱镜界面的入射角度,保证其在指定界面的全反射条件,采用精巧的棱镜分光结构实现三谱段分探测器实时成像；再结合水体及窗口材料介质的像差特性进行光学像差校正,完成水下微光彩色成像设计；该方法能够还原水下微光环境的彩色真实景象,实现水下成像系统的优化设计。(The invention relates to a full-sea deep low-light color imaging design method based on prism light splitting, which comprises the following steps: firstly, analyzing the cause of underwater aberration, determining the shape and material of an optical window, and manufacturing the optical window by adopting a toughened borosilicate glass concentric equal-thickness spherical cover with excellent optical performance and pressure resistance so as to ensure the energy utilization efficiency; designing a correction lens group and an imaging lens group according to parameters of an optical window to complete the design of an underwater special optical system with a long rear working distance; calculating and controlling the incident angle of light rays on a prism interface, ensuring the total reflection condition of the light rays on a designated interface, and realizing real-time imaging of a three-spectral-segment detector by adopting an exquisite prism beam splitting structure; then, optical aberration correction is carried out by combining the aberration characteristics of the water body and the window material medium, and the underwater low-light color imaging design is completed; the method can restore the color real scene of the underwater microlight environment and realize the optimal design of the underwater imaging system.)

1. An underwater low-light color imaging design method based on prism beam splitting is characterized by comprising the following steps:

step S1: analyzing the cause of underwater aberration, the law of refraction n when light passes through the interface of seawater, glass and air_wsinθ_w＝n_gsinθ_g＝n_asinθ_aAberration such as distortion and chromatic aberration, errors such as focusing error and field error are generated;

n is_w、n_g、n_aRespectively of sea water, glass, airRefractive index, theta_w、θ_g、θ_aRespectively the refraction angles in seawater, glass and air;

step S2: according to the underwater aberration characteristic and the specific application scene of underwater large-field imaging, the optical window is made of tempered high borosilicate glass material with excellent optical performance and pressure resistance, and the shape of the optical window is a concentric equal-thickness spherical cover;

step S3: calculating the focal length f' of the concentric equal-thickness spherical cover, adopting a short-focus objective lens as a correction lens group to compensate the refraction effect and the image surface curvature of the spherical cover, completing the basic underwater imaging design by matching with an imaging lens group with a long back working distance, and calculating the focal length of the spherical cover according to the following formula

Wherein n is_w、n_g、n_aRefractive index of sea water, glass, air, r₁、r₂Radius of curvature of the first face and the second face of the ball cover;

step S4: in order to give consideration to both low-light performance and color restoration, a beam splitter prism consisting of three optical wedges is placed at the position of a long back working distance of an imaging lens group, when light rays in corresponding wave bands need to meet the condition that an optically dense medium enters an optically sparse medium, the incident angles of the light rays are all larger than a total reflection angle theta (which is a satisfied formula in an air medium) so as to meet the separation of three primary colors, and the critical angle of total reflection is calculated according to the following formula:

θ＝arcsin(1/n)

wherein n is the refractive index of the prism medium;

step S5: in the prism design process, a quasi-telecentric light path is adopted to improve the uniformity of the image plane illumination, in the optimization design process, the maximum deflection angle delta in an incident light beam needs to be controlled in a key way,

the maximum deflection angle is related to the incident angle of the edge light, in the formula, θ is the total reflection angle of the light, so that the three-band light splitting of the RGB of the prism is realized, and the following conditions must be met:

β-δ＞θ_B；α+δ＜θ_R；

where β, α are two wedge angles of the first wedge, θ_B、θ_RThe critical angle of total reflection of red light and blue light, and delta is the maximum deflection angle of an incident light beam;

step S6: on the basis of the step S5, reasonable optical materials are adopted, system parameters are optimized under proper constraint conditions, aberration can be corrected in a balanced manner, and a design result of the underwater low-light-level color imaging system is obtained;

step S7: three low-light detectors used in cooperation with the prism are used for imaging the position of each pixel point, local colors are obtained in a non-interpolation mode, the image is closer to real colors,

and (3) the pixel sizes of the three micro light detectors are 6.5 mu m, and if the RMS and the MTF obtained in the step (6) do not meet the index requirements, the steps S3, S4 and S5 are repeated until the parameters meet the index requirements.

2. The underwater low-light-level color imaging design method based on prism splitting according to claim 1, characterized in that:

in the step S1, the focus error indicates that the underwater object distance L of the plane window becomes L₁From L₁In L/nW + d, the object distance is shortened by 25%, which increases the front focal length of the lens by about 4/3 times; the field error refers to the law of refraction n of the water-glass shell window-air interface_wsin H_w＝n_gsin H_g＝n_asin H_aReducing the field of view of the underwater imaging to about 1/3;

wherein H_w、H_g、H_aRespectively the refraction angle in seawater, glass and air.

3. The underwater low-light-level color imaging design method based on prism splitting according to claim 1, characterized in that:

in step S6, on the premise of ensuring the imaging quality and the transmittance of the operating spectrum, the design is performed by using common glasses of as few types as possible;

the transmittance of the optical material is more than 97% in a working wavelength band (400nm-650 nm).

4. The underwater low-light-level color imaging design method based on prism splitting according to claim 1, characterized in that:

in said step S7, the detector resolution is 2048 × 1152, the pixel size is 6.5 μm × 6.5 μm; the 3x6.5 μm CMOS is equivalent to an 11 μm monolithic CMOS in terms of photo-sensing area.

[ technical field ] A method for producing a semiconductor device

The invention relates to the technical field of photoelectric imaging systems, in particular to an underwater low-light-level color imaging design method based on prism light splitting.

[ background of the invention ]

The ocean covers 71 percent of the earth surface, mineral resources are rich, biological species are rich, energy reserves are huge, the optical imaging device has the characteristics of high resolution and in-situ recording, and comprehensive and detailed image data can be provided for researches on underwater ecological environment, benthic organism activity habits and the like.

The sea water has serious attenuation to visible light wave band, no natural light reaches deep sea, and only active illumination can be adopted. The optical system must fully utilize the limited platform illumination energy, and the color restoration and the low-light performance of underwater optical imaging are the first problems to be solved.

In the prior art, a conventional color detector filters colors by using a Bayer pattern, so that the utilization efficiency of spectral energy is limited; and the color obtained by interpolation of each pixel point also has deviation, and the scheme of a single detector cannot give consideration to both low-light and color performances.

The glimmer performance of traditional imaging equipment reaches under the prerequisite of sacrificing depth of field, though in radio and television and industrial application scene, the solution that the cross prism beam split spectrum section was gathered appears, nevertheless lacks the special optics mirror group design to the water medium, and current imaging equipment can't satisfy high-quality glimmer colour application demand under water.

[ summary of the invention ]

The invention aims to provide an underwater low-light color imaging design method based on prism beam splitting, which fully considers the contradiction between high dynamic imaging and color reduction of a low-light environment, analyzes beam splitting structure parameters, realizes optical system optimization design by matching with aberration characteristics of a water body and an optical window, and can accurately reduce the real scene of the underwater low-light environment.

In order to achieve the purpose, the underwater low-light color imaging design method based on prism beam splitting comprises the following steps:

step S1: analyzing the cause of underwater aberration, law of refraction n, when light passes through the sea-glass-air interface_wsinθ_w＝n_gsinθ_g＝n_asinθ_aAberration such as distortion and chromatic aberration, errors such as focusing error and field error are generated;

n_w、n_g、n_arefractive indices of seawater, glass, air, respectively, theta_w、θ_g、θ_aRespectively are seawater,Angle of refraction in glass, air;

step S2: according to the underwater aberration characteristic and the specific application scene of underwater large-field imaging, the optical window is made of tempered high borosilicate glass material with excellent optical performance and pressure resistance, and the shape of the optical window is a concentric equal-thickness spherical cover;

step S3: calculating the focal length f' of the concentric equal-thickness spherical cover, adopting a short-focus objective lens as a correction lens group to compensate the refraction effect and the image surface curvature of the spherical cover, completing the basic underwater imaging design by matching with an imaging lens group with a long back working distance, and calculating the focal length of the spherical cover according to the following formula

Wherein n is_w、n_g、n_aRefractive index of sea water, glass, air, r₁、r₂Radius of curvature of the first face and the second face of the ball cover;

step S4: in order to give consideration to both low-light performance and color restoration, a beam splitter prism consisting of three optical wedges is placed at the long back working distance position of an imaging lens group, light rays in corresponding wave bands must meet the condition that an optically dense medium enters an optically sparse medium, the incident angles of the light rays are all larger than a total reflection angle theta (which is a satisfied formula in an air medium) so as to meet the separation of three primary colors, and the critical angle of total reflection is calculated according to the following formula:

θ＝arcsin(1/n)

wherein n is the refractive index of the prism medium;

step S5: in the prism design process, a quasi-telecentric light path is adopted to improve the uniformity of the image plane illumination, in the optimization design process, the maximum deflection angle delta in an incident light beam needs to be controlled in a key way,

the maximum deflection angle is related to the incident angle of the edge light, in the formula, θ is the total reflection angle of the light, so that the three-band light splitting of the RGB of the prism is realized, and the following conditions must be met:

β-δ>θ_B；α+δ<θ_R；

wherein, beta and alpha are two wedge angles of the first optical wedge，θ_B、θ_RThe critical angle of total reflection of red light and blue light, and delta is the maximum deflection angle of an incident light beam;

step S6: on the basis of the step S5, reasonable optical materials are adopted, system parameters are optimized under proper constraint conditions, aberration can be corrected in a balanced manner, and a design result of the underwater low-light-level color imaging system is obtained;

step S7, three micro-light detectors used with the prism take part in imaging each pixel point position, local color is obtained by non-interpolation, the image is closer to real color,

and (3) pixel sizes of the three micro-light detectors are 6.5 mu m, and if the RMS and the MTF obtained in the step 6 do not meet the index requirements, the steps S3, S4 and S5 are repeated until the parameters meet the index requirements.

Preferably, in step S1, the focus error means that the plane window underwater object distance L becomes L₁From L₁In L/nW + d, the object distance is shortened by 25%, which increases the front focal length of the lens by about 4/3 times; the field error refers to the law of refraction n of the water-glass shell window-air interface_wsinH_w＝n_gsinH_g＝n_asinH_aReducing the field of view of the underwater imaging to about 1/3;

wherein H_w、H_g、H_aRespectively the refraction angle in seawater, glass and air.

Preferably, in step S6, on the premise of ensuring the imaging quality and the transmittance of the working spectrum, the design is performed by using a small number of types of common glass;

the transmittance of the optical material is more than 97% in a working wavelength band (400nm-650 nm).

Preferably, in step S7, the detector resolution is 2048 × 1152, and the pixel size is 6.5 μm × 6.5 μm; the 3x6.5 μm CMOS is equivalent to an 11 μm monolithic CMOS in terms of photo-sensing area.

The underwater low-light color imaging design method based on prism beam splitting has the following beneficial effects: the method fully considers the contradiction between high dynamic imaging and color reduction in the low-light environment; meanwhile, RGB three primary colors are separated by combining prism light splitting with a high-performance glimmer chip, and an underwater special optical system is adopted to design balanced aberration, so that real color restoration of an underwater glimmer environment is realized.

[ description of the drawings ]

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.

Fig. 1 is a schematic flow chart of an underwater low-light color imaging design method based on prism beam splitting according to an embodiment of the present invention;

FIG. 2 is a schematic view of the refraction of light through a planar window at the water-glass-air interface;

FIG. 3 is an object-image relationship of light passing through a glass plate;

FIG. 4 is a schematic diagram of prism tri-primary light splitting;

FIG. 5 is a three-dimensional view of a prism;

FIG. 6 shows the design result of underwater low-light color imaging;

FIG. 7 optical transfer function MTF >[email protected] lp/mm;

fig. 8 is an image plane dot diagram RMS.

[ detailed description ] embodiments

In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

The embodiment of the present invention will be further described in detail with reference to the accompanying drawings, and fig. 1 is a schematic flow chart of a design method of an underwater imaging system according to the embodiment of the present invention:

the method comprises the following steps:

in step S1: analyzing the cause of underwater aberration, law of refraction n, when light passes through the sea-glass-air interface_wsinθ_w＝n_gsinθ_g＝n_asinθ_aAberration such as distortion and chromatic aberration, errors such as focusing error and field error are generated;

wherein n is_w、n_g、n_aRefractive indices of seawater, glass, air, respectively, theta_w、θ_g、θ_aRespectively the refraction angle in seawater, glass and air.

Referring to FIG. 3, the focus error means that the underwater object distance L of the plane window becomes L₁From L₁L/nW + d, it is known that the object distance is shortened by 25%, the front focal length of the lens is increased by about 4/3 times, and the front focal length of the lens is increased by about 4/3 times under the water of the plane window;

the field error refers to the law of refraction n of the water-glass shell window-air interface_wsinH_w＝n_gsinH_g＝n_asinH_aThe field of view of the underwater imaging is reduced to about 1/3,

wherein H_w、H_g、H_aThe angles of view in seawater, glass and air respectively.

In step S2: according to the underwater aberration characteristic and the specific application scene of underwater large-field-of-view imaging, the optical window is made of tempered high borosilicate glass materials with excellent optical performance and compression resistance, the shape of the optical window is a concentric equal-thickness spherical cover, the transmittance of the 15 mm-thick tempered high borosilicate glass cover is higher than 93% in a visible light wave band, and parameters such as the compression strength of the tempered high borosilicate glass cover meet the working requirements of a myriameter underwater protection window.

Step S3: calculating the focal length f of the concentric equal-thickness spherical cover, adopting a short-focus objective lens as a correction lens group to compensate the refraction effect and the image surface curvature of the spherical cover, completing the basic underwater imaging design by matching with an imaging lens group with a long back working distance, and calculating the focal length of the spherical cover according to the following formula:

wherein n is_w、n_g、n_aRefractive index of sea water, glass, air, r₁、r₂Is the radius of curvature of the first and second faces of the spherical cap.

Step S4: in order to give consideration to low-light-level performance and color restoration, a beam splitter prism consisting of three optical wedges is placed at the long back working distance position of an imaging lens group, light rays in corresponding wave bands need to be transmitted into a light thinning medium by an optically dense medium, and the incident angles of the light rays are all larger than a total reflection angle theta (which is satisfied in an air medium) so as to satisfy the separation of three primary colors;

referring to fig. 4, the critical angle for total reflection is calculated according to the following formula: theta as arcsin (1/n)

Where n is the prism medium index of refraction.

Step S5: in the optimization design process, the maximum deflection angle in an incident light beam needs to be controlled in a key mode, and the maximum deflection angle is related to the incident angle of marginal rays and the aperture angle of an image space light beam;

referring to fig. 5, where θ is the total reflection angle of light, the following conditions must be satisfied to realize three-band RGB splitting of the prism: beta-delta>θ_B；α+δ<θ_R；

Air gaps are formed between the prisms, bonding surfaces are formed between the prisms, the first film is a long-pass filter film, the second film is a short-pass filter film, in the formula, theta is a light total reflection angle, and the splitting of the prisms must meet the following conditions;

surface A: theta 1 is 2 alpha-arcsinNA is more than or equal to arcsin (1/n); the blue light satisfies the total reflection,

b surface: α + arcsinNA < arcsin (1/n); the red and green light does not satisfy the total reflection,

c, surface C: gamma-alpha < arcsin (1/n); the green light does not satisfy the total reflection,

d surface: theta 2-alpha is more than or equal to arcsin (1/n); the red light satisfies the total reflection,

where β, α are the two wedge angles of the first wedge, θ_B、θ_RThe critical angle of total reflection of red light and blue light, delta the maximum deflection angle of incident light beam, and NA the numerical aperture.

Step 6: on the basis of the step S5, reasonable optical materials are adopted, and system parameters are optimized under appropriate constraint conditions, so that aberration can be corrected in a balanced manner, and a design result of the underwater low-light-level color imaging system is obtained, referring to fig. 6, 7 and 8;

wherein, four lens materials are selected: H-FK61(497816), H-K9L (517642), H-ZK14(603606), and F2 (620364).

And 7, imaging each pixel point position by three micro light detectors matched with the prism, obtaining local color by non-interpolation, enabling the image to be closer to real color, enabling the pixel size of the three micro light detectors to be 6.5 mu m, enabling RMS obtained in the step 6 to be smaller than 6.5 mu m and meeting the requirement of loose tolerance to be smaller than 6.5 mu m, enabling the MTF to be as high as possible at the sampling frequency @77lp/mm, and repeating the steps S3, S4 and S5 when the effect is poor until the parameters meet the indexes.

The above-mentioned serial numbers of the embodiments of the present invention are merely for description and do not represent the merits of the embodiments.

In the above embodiments of the present invention, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.

In summary, the underwater low-light color imaging design method based on prism beam splitting provided by the invention comprises the following steps: firstly, analyzing the cause of underwater aberration, determining the shape and material of an optical window, and manufacturing the optical window by adopting a toughened borosilicate glass concentric equal-thickness spherical cover with excellent optical performance and pressure resistance so as to ensure the energy utilization efficiency; designing a correction lens group and an imaging lens group according to parameters of an optical window to complete the design of an underwater special optical system with a long rear working distance; calculating and controlling the incident angle of light rays on a prism interface, ensuring the total reflection condition of the light rays on a designated interface, and realizing real-time imaging of a three-spectral-segment detector by adopting an exquisite prism beam splitting structure; then, optical aberration correction is carried out by combining the aberration characteristics of the water body and the window material medium, and the underwater low-light color imaging design is completed; the method can restore the color real scene of the underwater microlight environment and realize the optimized design of the underwater imaging system level.

In the embodiments provided in the present application, it should be understood that the disclosed technology can be implemented in other ways. The above-described embodiments of the apparatus are merely illustrative, and for example, a division of a unit may be a division of a logic function, and an actual implementation may have another division, for example, a plurality of units or components may be combined or may be integrated into another system, or some features may be omitted, or not executed, and in another point, the shown or discussed coupling or direct coupling or communication connection between each other may be through some interfaces, indirect coupling or communication connection between units or modules, and may be in an electrical or other form. (may be removed)

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.

The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a removable hard disk, a magnetic or optical disk, and other various media capable of storing program codes.

The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any way. It will be understood by those skilled in the art that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.