KR20230043734A - Design method for tolerance sensitivity reduction of 6P mobile lens system, apparatus and computer program for performing the design method - Google Patents

Abstract

A design method for reducing tolerance sensitivity of a 6P mobile optical system according to a preferred embodiment of the present invention, a device for performing the same, and a computer program are provided. By designing a 6P mobile optical system which increases expected production yield while reducing tolerance sensitivity, when choosing a material with an appropriate refractive index, tolerance sensitivity is reduced and the performance of the optical design is improved. Manufacturing costs can be reduced by increasing yield due to reduced tolerance sensitivity.

Description

Design method for tolerance sensitivity reduction of 6P mobile optical system, apparatus and computer program for performing the design method

The present invention relates to a design method for reducing tolerance sensitivity of a 6P mobile optical system, an apparatus and a computer program for performing the same, and more particularly, to a method, apparatus and computer program for designing an optical system for a mobile.

Recently, as the demand level of smartphone users increases, ultra-small and slim, high-performance image sensors and high-resolution lenses are required. In particular, sensitivity to tolerances generated in the manufacturing process is also increased, so that the problem of increasing cost in the manufacturing process continues to occur. Accordingly, by seeking and proceeding with the direction of the sensitivity reduction design, it is possible to reduce manufacturing cost by improving lens production productivity, maximize the performance of the lens system, and manage it within the range of desired performance. In order to satisfy this, It is necessary to properly set the tolerance of each lens. In addition, the performance of the lens to be actually manufactured can be predicted by performing tolerance analysis and estimating the yield before manufacturing the designed lens.

1 is a diagram for explaining MTF, and FIG. 2 is a diagram for explaining tolerance.

Tolerance is a value that determines the permissible dimensional change of variables and adjustment variables when producing lenses, and the permissible range is a value according to the production capacity of the company that manufactures the lens. If the designer sets the tolerance too small, the manufacturing cost may increase and the production yield may also decrease. Therefore, when designing, appropriate tolerances must be set to ensure desired performance targets are met and manufacturing and assembly costs can be minimized.

Setting an appropriate tolerance acts as an essential factor for cost reduction in mass production. Therefore, it is important to achieve a balance between performance and cost through tolerance analysis and setting. An analysis of the tolerances is necessary for proper tolerance allocation. Tolerance analysis methods can be largely divided into three types. First, it is the worst case (WC) model. The WC model is one of the simplest and most basic tolerance analyzes. This is a method of simply adding or subtracting each tolerance given from the designed lens data without considering the dispersion of tolerance values within the tolerance range. Second, it is a root sum of the square (RSS) model. This is a method of defining and expressing a function for the change in performance, assuming that the errors in the manufacturing process are independent within the corresponding range and form a normal distribution. A third method is a Monte Carlo simulation. Monte Carlo simulation is a method of analyzing the manufacturing performance and design performance of an optical system made by arbitrary values by generating random errors within the range of allowable tolerances with respect to the variables of the lens system.

Further, the design performance means basic performance when the dimensions of optical elements used in the optical system are standard dimensions. In other words, it refers to the theoretical performance before applying the tolerance of the optical system. On the other hand, manufacturing performance refers to performance when each dimension of optical elements exists within a set standard range, and refers to actual performance after applying tolerances to the optical system. Therefore, design performance and fabrication performance refer to different values.

In addition, tolerance sensitivity analysis can generally easily analyze the sensitivity of various design variables based on the MTF for the optical system, and obtain a performance distribution of the imaging optical system. Sensitivity analysis is to analyze the performance change of the optical system by artificially applying manufacturing and assembly errors to the theoretically designed optical system. That is, it refers to analyzing how sensitively the performance of an optical system responds to an error in the radius of curvature when manufacturing a lens, a center position error when assembling a lens, and a tilt error of a lens. Through this error tolerance, the allowable change in error is determined when designing the lens to satisfy the target performance while minimizing the manufacturing cost. If a large tolerance is set for a lens design that requires high precision, the desired performance will not be satisfied. Therefore, it is common to set appropriate tolerances and design to minimize the effect on tolerances as much as possible.

Tolerance analysis of Code-V has three methods: TOR (tolerance analysis for MTF and RMS), TOD (tolerance analysis for principal ray distortion aberration), and TOL (tolerance analysis for paraxial optical quantity and third-order aberration). Among them, TOR connects each parameter treated as tolerance using data obtained through ray tracing and the wavefront. It can analyze the tolerance of the optical system very quickly by directly calculating the effect of manufacturing and assembly errors on the MTF or RMS wavefront aberration. way you can In addition, compensators can be used to simulate the assembly and adjustment process in Code-V, and all parameters that can be defined as Code-V tolerances can be compensators. At this time, the compensator serves to minimize the change in performance due to tolerance during assembly and alignment by enabling a large tolerance while maintaining optical performance.

One of the two calculation methods of TOR is to check the performance tolerance of the system by the tolerance specified as the sensitivity mode, and the other is to check the tolerance level and system for the performance variation specified as the inverse mode. It confirmed the performance tolerance of . In the case of the inverse sensitivity mode, it is a method used when there is no information about the tolerance. Code-V provides probabilistic information of various MTF and RMS values for the performance of the optical system through this method.

TOR is calculated by the following [Equation 1] as the change in MTF versus tolerance item ΔP.

TOR is the RMS wavefront aberration versus change in tolerance item ΔP is calculated by [Equation 2] below.

Here, TOR determines A and B coefficients for each tolerance and compensator in each field, and C coefficient corresponds to the basic performance and is the normal (nominal, ΔP=0) value of MTF or RMS ² (deviation). 1 is a graph of MTF versus change ΔP in tolerance terms. Here, in the case of rotationally symmetrical tolerances, the MTF curve is not always at the center of tolerance values. And, in the case of rotationally asymmetric tolerance, the MTF curve is generally centered on the tolerance value.

The tolerances used to design lenses considering manufacturing performance are as follows. Tolerances for surfaces include radius of curvature (r), index of refraction (n), and thickness (t). Tolerances for lenses include edge thickness. Tolerances related to lens alignment include eccentricity and tilt, etc. The following content shows the types of tolerances used in the present invention, each of which is defined as follows, and the content in parentheses refers to a command for the Code-V program.

(1) Delta refractive index (DLN): Tolerance for the refractive index of a surface

(2) Abbe-number delta (DLV): Tolerance for Abbe-number of face

(3) Lens thickness (DLT): Tolerance for the thickness of glass and air (Fig. 2 (a))

(4) Surface decenter (DLY): Tolerance of eccentricity between lens and optical axis (Fig. 2 (b))

(5) Surface tilt (DLA): Tolerance for the tilt of the lens surface (Fig. 2 (c))

(6) Lens group decenter (DSY): Tolerance for lens decenter ((d) in FIG. 2)

(7) Axial displacement (DSZ): Tolerance for the amount of movement on the z-axis ((e) in FIG. 2)

(8) Lend group tilt (BTY): Tolerance for lens tilt (Fig. 2 (f))

(9) Zernike Sag (ZFR): Tolerance for surface sag at the fringe wavelength over the entire effective aperture

And, the MTF (Modualtion Transfer Function) is an indicator used to express the performance of an optical system as a general numerical value. The MTF value indicates the degree to which the original of the subject can pass through the optical system and be expressed as an image that is actually formed on the image. For an ideal lens, the MTF value would be 1. The MTF number indicates the resolving power and contrast performance of a lens as an objective number, and in most cases, a lens with a high MTF number shows excellent images. There may be several ways to represent the MTF, but it is common to represent it as an MTF graph for spatial frequencies. At spatial frequency [line pair per mm], a line pair is a pair of lines and spaces. For example, 40 lp/mm means 40 lines in 1 mm. Among optical equipment, there is equipment that can measure the MTF value, and this measurement is usually measured with a reference chart that can be used as a standard. The MTF value varies depending on the degree of density of the bar, that is, the spatial frequency, and has different values depending on the horizontal and vertical directions. In general, if there is a lens with an MTF value close to '1' in the dense central part, it means that the lens is a lens with excellent resolution capable of depicting fine parts of the image well.

An object of the present invention is to provide a design method for reducing the tolerance sensitivity of a 6P mobile optical system, a device for performing the same, and a computer program for designing a 6P mobile optical system in which the tolerance sensitivity is reduced while the expected production yield is increased.

Other non-specified objects of the present invention may be additionally considered within the scope that can be easily inferred from the following detailed description and effects thereof.

A design method for reducing tolerance sensitivity of a 6P mobile optical system according to a preferred embodiment of the present invention for achieving the above technical problem includes setting a basic optical system based on a 6P mobile optical system using a preset design target optical system; Evaluating performance of the basic optical system; analyzing tolerance sensitivity of the basic optical system; Acquiring a redesigned optical system by redesigning the basic optical system by changing a material for at least one lens of the basic optical system based on a tolerance sensitivity analysis result of the basic optical system; Evaluating performance of the redesigned optical system; Analyzing tolerance sensitivity of the redesigned optical system and analyzing expected production yield and distortion change for the basic optical system and the redesigned optical system using Monte Carlo simulation; And redesigning the redesigned optical system using a tolerance sensitivity result according to a change in refractive index of at least one lens of the redesigned optical system based on the analysis result of tolerance sensitivity, expected production yield, and distortion change for the redesigned optical system. Acquiring a final optical system; includes.

Here, the design target optical system may have pixels of 13.2M, an F/# of 1.9, an angle of view of 78°, an effective focal length (EFL) of 3.51mm, and an optical system including six lenses.

Here, in the basic optical system performance evaluation step, based on the design target optical system, aberration analysis, MTF (Modulation Transfer Function) performance evaluation, and relative illumination (RI) analysis are performed to evaluate the performance of the basic optical system The step of analyzing tolerance sensitivity of the basic optical system may include analyzing tolerance sensitivity of the basic optical system for shape sensitivity, unit sensitivity, and assembly sensitivity.

Here, the basic optical system performance evaluation step performs aberration analysis on the basic optical system by analyzing aberrations including spherical aberration, astigmatism, and distortion aberration, and analyzes the MTF with a spatial frequency of 1101p/mm to obtain the basic The MTF performance evaluation for the optical system is performed, and the peripheral luminance ratio (RI) indicating the degree of darkness of the outer center of the image surface is analyzed to perform the RI analysis for the basic optical system. In the basic optical system tolerance sensitivity analysis step, the sensitivity to Zernike Sag is analyzed to analyze the shape sensitivity to the basic optical system, and based on lens thickness, surface decenter, and surface tilt Sensitivity of a single unit of the basic optical system may be analyzed, and assembly sensitivity of the basic optical system may be analyzed based on lens decenter, lens tilt, and axial displacement.

Here, in the redesigned optical system acquisition step, the sensitivity to the refractive index and Abbe number of the material of the basic optical system is analyzed, and the sensitivity to the refractive index and Abbe number of the material is analyzed for at least one lens of the basic optical system. The basic optical system may be redesigned by changing the material to a material having a high refractive index.

Here, the performance evaluation step of the redesigned optical system consists of evaluating the performance of the redesigned optical system by performing aberration analysis, MTF performance evaluation, and RI analysis, and the redesigned optical system tolerance sensitivity analysis step comprises: , Tolerance sensitivity of the redesigned optical system is analyzed for tolerances identified as MTF variation of 30% or more based on the tolerance sensitivity analysis result for the basic optical system, and is set to proceed in the transverse direction of the optical axis, and the spatial frequency is 1101p / mm The expected production yield for each of the basic optical system and the redesigned optical system is analyzed based on an MTF of 30% using Monte Carlo simulation with This can be done by analyzing

Here, in the final optical system acquisition step, a material having a different refractive index is applied to at least one lens of the redesigned optical system, and a change in tolerance sensitivity to a change in refractive index is compared using a Monte Carlo simulation, and the redesign is performed based on the comparison result. The final optical system may be obtained by changing at least one lens of the design optical system to a material having a high refractive index.

Here, in the final optical system acquisition step, the expected production yield and refractive index change for each of the plurality of redesigned optical systems to which a plurality of materials having refractive indices different from those of the basic optical system are applied based on an MTF of 30% using Monte Carlo simulation. It can be made by comparing tolerance sensitivity changes according to .

A computer program according to a preferred embodiment of the present invention for achieving the above technical problem is stored in a computer readable storage medium and executes any one of the design methods for reducing the tolerance sensitivity of the 6P mobile optical system on a computer.

A design device for reducing the tolerance sensitivity of a 6P mobile optical system according to a preferred embodiment of the present invention for achieving the above technical problem is a design device for performing a design for reducing the tolerance sensitivity of a 6P mobile optical system. a memory storing one or more programs for performing a design for reducing sensitivity; and one or more processors performing an operation for performing a design for tolerance sensitivity reduction of a 6P mobile optical system according to the one or more programs stored in the memory, wherein the processor performs a 6P optical system using a preset design target optical system. A basic optical system based on a mobile optical system is set, performance of the basic optical system is evaluated, tolerance sensitivity of the basic optical system is analyzed, and at least one lens of the basic optical system is analyzed based on a tolerance sensitivity analysis result for the basic optical system. The basic optical system is redesigned through material change to obtain a redesigned optical system, the performance of the redesigned optical system is evaluated, tolerance sensitivity of the redesigned optical system is analyzed, and Monte Carlo simulation is used to obtain the redesigned optical system. Analyzing the expected production yield and distortion change for the basic optical system and the redesigned optical system, and at least one of the redesigned optical system based on the analysis results of tolerance sensitivity, expected production yield and distortion change for the redesigned optical system. A final optical system is obtained by redesigning the redesigned optical system using a tolerance sensitivity result according to a change in the refractive index of the lens.

Here, the design target optical system may have pixels of 13.2M, an F/# of 1.9, an angle of view of 78°, an effective focal length (EFL) of 3.51mm, and an optical system including six lenses.

Here, the processor evaluates the performance of the basic optical system by performing aberration analysis, MTF (Modulation Transfer Function) performance evaluation, and Relative Illumination (RI) analysis based on the design target optical system, and shape sensitivity , it is possible to analyze the tolerance sensitivity of the basic optical system for single-unit sensitivity and assembly sensitivity.

Here, the processor performs aberration analysis on the basic optical system by analyzing aberrations including spherical aberration, astigmatism, and distortion aberration, and analyzes the MTF with a spatial frequency of 1101p/mm to obtain the MTF for the basic optical system Perform performance evaluation, analyze the ambient light ratio (RI) for the basic optical system by analyzing the ambient light ratio (RI), which indicates the degree of darkness of the outside of the center of the image, and analyze the sensitivity to Zernike Sag Analyze the shape sensitivity of the basic optical system, and analyze the unit sensitivity of the basic optical system based on lens thickness, surface decenter, and surface tilt, and lens decenter ), lens tilt and axial displacement, it is possible to analyze the assembly sensitivity of the basic optical system.

According to a design method for reducing tolerance sensitivity of a 6P mobile optical system according to a preferred embodiment of the present invention, a device for performing the same, and a computer program, by designing a 6P mobile optical system in which tolerance sensitivity is reduced while expected production yield is increased, Material selection can reduce tolerance sensitivity, improve the performance of optical designs, and reduce manufacturing costs through increased yield due to reduced tolerance sensitivity.

The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description below.

1 is a diagram for explaining MTF.
2 is a diagram for explaining tolerances.
3 is a block diagram illustrating a design device for reducing tolerance sensitivity of a 6P mobile optical system according to a preferred embodiment of the present invention.
4 is a flowchart illustrating a design method for reducing tolerance sensitivity of a 6P mobile optical system according to a preferred embodiment of the present invention.
5 is a diagram for explaining a design target optical system according to a preferred embodiment of the present invention.
6 is a view for explaining the layout of a basic optical system according to a preferred embodiment of the present invention.
7 is a diagram for explaining lens characteristics of a basic optical system according to a preferred embodiment of the present invention.
8 is a diagram for explaining the lens aspheric coefficient of the basic optical system according to a preferred embodiment of the present invention.
9 is a diagram showing results of aberration analysis of a basic optical system according to a preferred embodiment of the present invention.
10 is a diagram showing MTF performance evaluation results for each field according to a preferred embodiment of the present invention.
11 is a diagram showing an MTF curve of a basic optical system according to a preferred embodiment of the present invention.
12 is a diagram showing the result of analyzing the ambient light ratio of the basic optical system according to a preferred embodiment of the present invention.
13 is a diagram for explaining types and application ranges of tolerances according to a preferred embodiment of the present invention.
14 is a diagram showing MTF sensitivity to surface tilt (DLA) of a basic optical system according to a preferred embodiment of the present invention.
15 is a diagram showing MTF sensitivity to lens group tilt (BTY) of a basic optical system according to a preferred embodiment of the present invention.
16 is a diagram showing MTF sensitivity to lens group decenter (DSY) of a basic optical system according to a preferred embodiment of the present invention.
17 is a diagram showing MTF sensitivity to displacement (DSZ) of a basic optical system according to a preferred embodiment of the present invention.
18 is a diagram showing MTF sensitivity to Zernike coefficient z8 of a basic optical system according to a preferred embodiment of the present invention.
19 is a diagram showing MTF sensitivity to Zernike coefficient z9 of a basic optical system according to a preferred embodiment of the present invention.
20 is a diagram showing the MTF sensitivity to the refractive index of each material according to a preferred embodiment of the present invention.
21 is a diagram showing the MTF sensitivity to the Abbe number of each material according to a preferred embodiment of the present invention.
22 is a diagram for explaining lens characteristics of a redesigned optical system according to a preferred embodiment of the present invention.
23 is a diagram for explaining the layout of a redesigned optical system according to a preferred embodiment of the present invention.
24 is a diagram for explaining lens aspheric coefficients of a redesigned optical system according to a preferred embodiment of the present invention.
25 is a diagram showing the results of aberration analysis of the redesigned optical system according to a preferred embodiment of the present invention.
26 is a diagram showing MTF performance evaluation results for each field of the redesigned optical system according to a preferred embodiment of the present invention.
27 is a diagram showing an MTF curve of a redesigned optical system according to a preferred embodiment of the present invention.
28 is a diagram showing the result of analyzing the ambient light ratio of the redesigned optical system according to a preferred embodiment of the present invention.
29 is a diagram showing MTF sensitivity to lens group decenter (DSY) of the redesigned optical system according to a preferred embodiment of the present invention.
30 is a diagram showing MTF variation and deviation for each field with respect to lens #1 decenter according to a preferred embodiment of the present invention.
31 is a diagram showing MTF sensitivity to lens group tilt (BTY) of the redesigned optical system according to a preferred embodiment of the present invention.
32 is a diagram showing MTF sensitivity to displacement (DSZ) of a redesigned optical system according to a preferred embodiment of the present invention.
33 is a diagram showing MTF sensitivity to Zernike coefficient z8 of the redesigned optical system according to a preferred embodiment of the present invention.
34 is a diagram showing MTF sensitivity to Zernike coefficient z9 of the redesigned optical system according to a preferred embodiment of the present invention.
35 is a diagram showing Monte Carlo simulation comparison results for each field according to a preferred embodiment of the present invention.
36 is a diagram showing Monte Carlo simulation results of a basic optical system and a redesigned optical system according to a preferred embodiment of the present invention.
37 is a diagram showing a distortion change amount with respect to tolerance sensitivity according to a preferred embodiment of the present invention.
38 is a diagram showing refractive indices and Monte Carlo simulation results for each EP series material according to a preferred embodiment of the present invention.
39 is a diagram showing the refractive index and expected production yield for each EP material according to a preferred embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Advantages and features of the present invention, and methods of achieving them, will become clear with reference to the detailed description of the following embodiments taken in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and only the present embodiments make the disclosure of the present invention complete, and are common in the art to which the present invention belongs. It is provided to fully inform the knowledgeable person of the scope of the invention, and the invention is only defined by the scope of the claims. Like reference numbers designate like elements throughout the specification.

Unless otherwise defined, all terms (including technical and scientific terms) used in this specification may be used in a meaning commonly understood by those of ordinary skill in the art to which the present invention belongs. In addition, terms defined in commonly used dictionaries are not interpreted ideally or excessively unless explicitly specifically defined.

In this specification, terms such as "first" and "second" are used to distinguish one component from another, and the scope of rights should not be limited by these terms. For example, a first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

In this specification, identification codes (e.g., a, b, c, etc.) for each step are used for convenience of explanation, and identification codes do not describe the order of each step, and each step is clearly a specific order in context. Unless specified, it may occur in a different order from the specified order. That is, each step may occur in the same order as specified, may be performed substantially simultaneously, or may be performed in the reverse order.

In this specification, expressions such as “has”, “can have”, “includes” or “can include” indicate the existence of a corresponding feature (eg, numerical value, function, operation, or component such as a part). indicated, and does not preclude the presence of additional features.

Hereinafter, with reference to the accompanying drawings, a design method for reducing tolerance sensitivity of a 6P mobile optical system according to the present invention, a device for performing the same, and a preferred embodiment of a computer program will be described in detail.

First, with reference to FIG. 3, a design apparatus for reducing tolerance sensitivity of a 6P mobile optical system according to a preferred embodiment of the present invention will be described.

3 is a block diagram illustrating a design device for reducing tolerance sensitivity of a 6P mobile optical system according to a preferred embodiment of the present invention.

Referring to FIG. 3, a design device (hereinafter referred to as a 'design device') 100 for reducing tolerance sensitivity of a 6P mobile optical system according to a preferred embodiment of the present invention is a 6P mobile with reduced tolerance sensitivity and increased expected production yield. design the optics.

That is, the present invention compares the tolerance sensitivities of materials having different refractive indices for the 6P mobile optical system and uses a material having a high refractive index, thereby obtaining a result in which the expected production yield increases linearly while the tolerance sensitivities decrease. Accordingly, the present invention can reduce the tolerance sensitivity and improve the performance of optical design by selecting a material having an appropriate refractive index. In addition, the present invention can reduce the manufacturing cost due to the increase in yield due to the decrease in tolerance sensitivity.

To this end, the design device 100 may include one or more processors 110, a computer readable storage medium 130, and a communication bus 150.

The processor 110 may control the design device 100 to operate. For example, the processor 110 may execute one or more programs 131 stored in the computer readable storage medium 130 . The one or more programs 131 may include one or more computer executable instructions, and the computer executable instructions, when executed by the processor 110, cause the design device 100 to design for reducing the tolerance sensitivity of the 6P mobile optical system. It may be configured to perform an operation for performing.

The computer-readable storage medium 130 is configured to store computer-executable instructions or program code, program data, and/or other suitable form of information for performing a design for tolerance sensitivity reduction of a 6P mobile optical system. The program 131 stored in the computer readable storage medium 130 includes a set of instructions executable by the processor 110 . In one embodiment, computer readable storage medium 130 may include memory (volatile memory such as random access memory, non-volatile memory, or a suitable combination thereof), one or more magnetic disk storage devices, optical disk storage devices, flash It may be memory devices, other types of storage media that can be accessed by the design device 100 and store desired information, or a suitable combination thereof.

The communication bus 150 interconnects various other components of the design device 100, including the processor 110 and the computer readable storage medium 130.

Design device 100 may also include one or more input/output interfaces 170 and one or more communication interfaces 190 providing interfaces for one or more input/output devices. The input/output interface 170 and the communication interface 190 are connected to the communication bus 150 . An input/output device (not shown) may be connected to other components of the design device 100 through an input/output interface 170 .

Next, a design method for reducing tolerance sensitivity of a 6P mobile optical system according to a preferred embodiment of the present invention will be described with reference to FIG. 4 .

4 is a flowchart illustrating a design method for reducing tolerance sensitivity of a 6P mobile optical system according to a preferred embodiment of the present invention.

Referring to FIG. 4 , the processor 110 of the design device 100 may set a basic optical system based on a 6P mobile optical system using a preset design target optical system (S110).

Here, the design target optical system may have pixels of 13.2M, an F/# of 1.9, an angle of view of 78°, an effective focal length (EFL) of 3.51mm, and an optical system including six lenses.

Then, the processor 110 may evaluate the performance of the basic optical system (S120).

That is, the processor 110 may evaluate the performance of the basic optical system by performing aberration analysis, modulation transfer function (MTF) performance evaluation, and relative illumination (RI) analysis based on the design target optical system.

More specifically, the processor 110 may analyze aberrations including spherical aberration, astigmatism, and distortion aberration to perform aberration analysis on the basic optical system.

In addition, the processor 110 may perform MTF performance evaluation on the basic optical system by analyzing the MTF at a spatial frequency of 1101p/mm.

In addition, the processor 110 may perform the RI analysis on the basic optical system by analyzing the RI, which indicates the degree of darkness of the outside of the center of the image surface.

Then, the processor 110 may analyze tolerance sensitivity of the basic optical system (S130).

That is, the processor 110 may analyze tolerance sensitivity of the basic optical system for shape sensitivity, unit sensitivity, and assembly sensitivity.

In more detail, the processor 110 may analyze the shape sensitivity of the basic optical system by analyzing the sensitivity to Zernike Sag.

In addition, the processor 110 may analyze the sensitivity of the unit to the basic optical system based on the lens thickness, surface decenter, and surface tilt.

Also, the processor 110 may analyze the assembly sensitivity of the basic optical system based on lens decenter, lens tilt, and axial displacement.

Then, the processor 110 may obtain a redesigned optical system by redesigning the basic optical system (S150).

That is, the processor 110 may obtain a redesigned optical system by redesigning the basic optical system by changing the material of at least one lens of the basic optical system based on the tolerance sensitivity analysis result of the basic optical system.

In more detail, the processor 110 may analyze the refractive index of the material of the basic optical system and the sensitivity to the Abbe number.

Further, the processor 110 may redesign the basic optical system by changing the material for at least one lens of the basic optical system to a material having a high refractive index based on the sensitivity analysis result for the refractive index and Abbe's number of the material.

Then, the processor 110 may evaluate the performance of the redesigned optical system (S150).

That is, the processor 110 may evaluate the performance of the redesigned optical system by performing aberration analysis, MTF performance evaluation, and RI analysis.

Then, the processor 110 may analyze tolerance sensitivity of the redesigned optical system, and analyze expected production yield and distortion change for the basic optical system and the redesigned optical system (S160).

That is, the processor 110 may analyze tolerance sensitivity of the redesigned optical system.

In more detail, the processor 110 may analyze the tolerance sensitivity of the redesigned optical system for a tolerance identified as an MTF variation of 30% or more based on the tolerance sensitivity analysis result of the basic optical system.

In addition, the processor 110 may analyze expected production yield and distortion change for the basic optical system and the redesigned optical system using Monte Carlo simulation.

In more detail, the processor 110 is set to proceed in the transverse direction of the optical axis and the expected production for each of the basic optical system and the redesigned optical system based on an MTF of 30% using Monte Carlo simulation with a spatial frequency of 1101 p / mm yield can be analyzed.

Also, the processor 110 may analyze a distortion change for each of the basic optical system and the redesigned optical system using Monte Carlo simulation.

Thereafter, the processor 110 may obtain a final optical system by redesigning the redesigned optical system (S170).

That is, the processor 110 performs the redesigned optical system by using the tolerance sensitivity result according to the refractive index change of at least one lens of the redesigned optical system based on the tolerance sensitivity of the redesigned optical system, the expected production yield, and the analysis result of the distortion change. The final optics can be obtained by redesigning.

More specifically, the processor 110 may apply materials having different refractive indices to at least one lens of the redesigned optical system and compare tolerance sensitivity changes to refractive index changes using Monte Carlo simulation.

For example, the processor 110 calculates an expected production yield for each of a plurality of redesigned optical systems to which a plurality of materials having refractive indices different from those of the basic optical system are respectively applied based on an MTF of 30% using Monte Carlo simulation and tolerance sensitivity according to a change in refractive index changes can be compared.

Also, the processor 110 may acquire a final optical system by changing at least one lens of the redesigned optical system to a material having a high refractive index based on the comparison result.

Next, an example of a design method for reducing tolerance sensitivity of a 6P mobile optical system according to a preferred embodiment of the present invention will be described with reference to FIGS. 5 to 39 .

A. Basic optics reproduction and optimization

In the present invention, among the mobile optical system patents, a low F/# of 1.9, stable aberration performance, and low tolerance sensitivity plastic 6 patents are selected and reproduced as the basic optical system, and MTF (modulation transfer function) performance and relative illumination , RI), etc., and analyze the tolerance sensitivity according to the MTF change amount.

A-1. Basic optics reproduction and optimization

5 is a view for explaining a design target optical system according to a preferred embodiment of the present invention, FIG. 6 is a view for explaining the layout of a basic optical system according to a preferred embodiment of the present invention, and FIG. 7 is a view for explaining the present invention. is a diagram for explaining lens characteristics of a basic optical system according to a preferred embodiment of the present invention, and FIG. 8 is a diagram for explaining lens aspheric coefficients of a basic optical system according to a preferred embodiment of the present invention.

The present invention aims to design a smartphone camera optical system corresponding to 13.2M pixels. With the development of semiconductor technology, the demand for lenses targeting high specifications is also increasing according to the high-density CMOS image sensor (CIS). Therefore, F/# is set to 1.9, and the angle of view is designed to be 78˚ to have a wide range of angles of view, and the EFL is determined to be 3.51mm. In addition, the overall length is set to 4.52mm, and the lens design goal is set so that it can be used for mobile cameras, and the design is progressed. Details of the design goal are shown in FIG. 5 .

The CIS chosen to design the 13M camera lens chose Sony's 1/3-inch S5K3J1SX. This sensor supports 1080p HD video shooting at 30fps and 60fps and has full resolution 4K high-definition performance. It has the effective number of pixels of 4224(H) x 3136(V) and the pitch of one pixel has the size of 1.12um x 1.12um. The size of the entire image plane is 4.73mm x 3.51mm.

The present invention sets a basic optical system using the optical system disclosed in US Patent Publication No. 2018-0203208 (hereinafter referred to as 'patent optical system'). The patented optical system consists of 6 plastic lenses and is designed to be suitable for mobile cameras by designing an IR cutoff filter in front of the sensor. And all surfaces are designed as a lens having an aspherical shape. The patented optical system is a representative optical system that has stable power of positive (+) on surface #1, negative (-) on #2, and positive (+) and negative (-) on surfaces #5 and #6, respectively.

Recently, a mobile optical system is being developed in a direction of minimizing an effective focal length (EFL) and a total track length (TTL) for a low F/# and a compact optical system for shooting in low light. Therefore, in the present invention, optimization is performed by selecting a patented optical system having a low F/# of 1.9 and a low EFL of 3.5 mm.

In addition, the OAL (overall all length) is fixed to 4.7 mm or less, the minimum thickness of the lens is 0.2 mm, and the conic constant (k) is also set to 90 or less. AOI (angle of incident) is set for CRA with the sensor, and optimization is performed based on distortion, LSA (lens surface angle), and FBL (flange back length).

6 is a layout of the basic optical system obtained by optimizing the patented optical system. Set vignetting on surfaces #2, #4 and #8 to minimize ray tracing error while optimizing.

7 is data on the primary characteristics of a basic optical system, that is, an initially designed lens. Both sides of a total of six plastic lenses are composed of an aspheric surface and a Qcon-aspheric surface. F/# is 1.92, which does not change significantly compared to the patented optical system, and TTL is 4.52mm, which is designed to be sufficiently used as a mobile camera optical system.

The material used in the basic optical system is plastic for all lenses except for the IR-cutoff filter. Lens #1 and lens #3 use APL5514, a material with a low refractive index, and all others use a material with a high refractive index from Mitsubishi's EP series. .

The IR-cutoff filter is 'D263T' and is configured to prevent light other than visible light from entering the sensor by using a glass material. In addition, in order to reflect errors that occur during actual production and assembly, the design is based on 3.0mm by applying an extra space of 0.1mm rather than the image height of 2.90mm.

8 shows aspheric coefficients of the basic optical system. Lens #1 to lens #4 are 16th order coefficients, and lens #5 and lens #6 use Qcon asphere to apply up to 20th order coefficients.

A-2. performance evaluation

9 is a diagram showing the aberration analysis result of the basic optical system according to a preferred embodiment of the present invention, FIG. 10 is a diagram showing the MTF performance evaluation result for each field according to a preferred embodiment of the present invention, and FIG. Figure 12 is a diagram showing the MTF curve of the basic optical system according to a preferred embodiment, Figure 12 is a view showing the ambient light ratio analysis result of the basic optical system according to a preferred embodiment of the present invention, Figure 13 is a view showing the 14 is a diagram showing the MTF sensitivity to surface tilt (DLA) of a basic optical system according to a preferred embodiment of the present invention, and FIG. 16 is a diagram showing the MTF sensitivity to lens group tilt (BTY) of the basic optical system according to a preferred embodiment of the present invention, and FIG. ) (DSY), Figure 17 is a diagram showing the MTF sensitivity to the displacement (DSZ) of the basic optical system according to a preferred embodiment of the present invention, Figure 18 is a diagram showing the preferred embodiment of the present invention 19 is a diagram showing the MTF sensitivity to Zernike coefficient z9 of the basic optical system according to a preferred embodiment of the present invention.

For performance evaluation, aberration analysis, MTF performance evaluation, and ambient light ratio are reviewed to determine whether the optical design goal shown in FIG. 5 is satisfied using Code-V, and tolerance sensitivity analysis for each shape sensitivity, unit sensitivity, and assembly sensitivity is performed. proceed with

A-2-1. aberration analysis

9 is a graph showing spherical aberration, astigmatism, and distortion aberration.

Spherical aberration and astigmatism show stable aberration within 0.1 in all wavelength ranges, distortion aberration satisfies the performance within 2%, and TV-distortion satisfies within 1% of the performance specification at about 0.25%. Here, TV-distortion is half the value obtained by subtracting 0.6 field distortion from full field distortion, and represents distortion on the screen by the degree of warping of the image on the diagonal compared to the short side of the image.

In general, optical distortion is used, but TV-distortion is mainly used in mobile camera optics. In other optical systems, distortion of the curved shape occurs because only the curvature of the front of the lens is regarded as a group and the image is formed. If the TV-distortion is within 1%, the human eye sees the image as a flat plane with little distortion.

A-2-2. MTF (Modulation Transfer Function)

The most commonly used number to evaluate the performance of a lens is the MTF. When the format of the sensor is 1/3 inch, it can be confirmed that Nyquist frequency = 1 / (2 × Pixel Size) = 446lp/mm and the reference spatial frequency is Nyquist/4 = 1115lp/mm.

In general, since the spatial frequency for performance evaluation is input in units of '5', it is evaluated based on 110 lp/mm in the present invention. 10 confirms that all fields have an MTF of 50% or more at 110 [lp/mm], which is Nyquist/4.

The larger the value of the spatial frequency expressed on the X-axis, the greater the number of light and dark line pairs coming within 1 mm. Therefore, in the case of a lens with a large MTF, resolution is improved.

11 shows the MTF curve of MTF performance. In the graph, the dotted line and the solid line are MTF performance values in the sagittal direction and the tangential direction, respectively. It can be seen that it does not give

A-2-3. Relative Illumination (RI)

The ambient light ratio (RI) refers to the degree of darkness of the periphery of the center of the top surface. It is calculated as the ratio of the exit pupil area on the off-axis to the exit pupil area on the axis, and the unit is [%], and the calculation result is shown in FIG. Here, 1.1F gives an extra margin of 0.1mm to the image height, and since it is to check the linearity of the RI, there is no effect on performance.

A-3. Tolerance Sensitivity Analysis

Sensitivity analysis is to determine how much the MTF changes with respect to the tolerance by declaring a tolerance for a specific value among various values of the designed lens. If the performance is greatly influenced by the tolerance, the sensitivity will be large. To check this sensitivity, a tolerance range must be set. In the present invention, the tolerance sensitivity is analyzed based on the sensitivity of 30% of the MTF change amount.

The types and ranges of tolerances used in the present invention are shown in FIG. 13 .

In the case of shape sensitivity, the sensitivity to Zernike Sag is analyzed, and the sensitivity of a single product is set by considering the thickness of the lens and the decenter and tilt of the surface. Lastly, the tolerance sensitivity is confirmed by setting the range of the eccentricity, tilt, and axial movement of the lens as the assembly sensitivity. Here, eccentricity and tilt can occur simultaneously in the x, y, and z-axis directions of the optical system, but due to the symmetry of the lens, only the tangential direction of the optical axis is considered for tolerance.

14 and 15 are the sensitivities confirmed by the MTF change amount for the tilt of each lens and surface. In the case of the tilt of the lens surface, the sensitivity of surfaces #1 and #5 is relatively high, and in the case of a lens, the sensitivity of lens #1 is high. high can be seen.

16 is a result of confirming the sensitivity with the amount of MTF variation for each lens' eccentricity. Based on the MTF variation of 30%, it is confirmed that the sensitivity of lens #1 and lens #2 is high, and in the case of lens #5, only 1.0 field is high.

17 is the sensitivity confirmed by the amount of MTF change with respect to the amount of movement on the z-axis of the lens, and it can be seen that the result of lens #2 is high.

18 and 19 show the result of confirming the sensitivity based on the MTF change amount according to each tolerance for each field. Looking at the results of Zernike coefficient z8 & z9, it shows the relatively highest sensitivity and can confirm the maximum 50% MTF change. Overall, when looking at the Zernike sag tolerance sensitivity results, the sensitivity to astigmatism and coma aberration of the z4 ~ z7 coefficients is confirmed to be around 10% of the MTF change, but the spherical aberration of the z8 and z9 coefficients is the change in sensitivity from the 1st surface to the 5th surface found to be higher than 30%.

So far, the sensitivity of the basic optical system, which has been optimized by considering only the performance of the patented optical system, has been analyzed for the tolerances defined and set above. Among the total 8 tolerances, when looking at the Zernike Sag tolerance sensitivity results, the sensitivity to astigmatism and coma aberration of z4 ~ z7 coefficients was confirmed to be around 10% of the MTF change, but the spherical aberration of z8 and z9 coefficients was found to be from surface #1 to surface #1. Up to #5, the change in sensitivity is confirmed to be higher than 30%. In addition, a sensitivity of more than 30% of the MTF change was confirmed in the centrality of the lens group, the tilt of each lens and lens surface, the thickness of the lens, and the displacement, and it can be seen that it has a large effect on the tolerance sensitivity.

In the next chapter B, the tolerance sensitivity is reduced by reducing the MTF variation per field to within 30% for the above 7 tolerances, and the tolerance sensitivity and distortion sensitivity for the MTF variation are compared. And, for more quantitative evaluation, the expected production yield using Monte Carlo simulation is compared and analyzed. In addition, in order to analyze the effect of sensitivity according to the change of refractive index, the effect on sensitivity is investigated by redesigning the optical system by applying all materials of the EP series.

B. Tolerance Sensitivity Reduction Design and Analysis

In this chapter, based on the results of tolerance sensitivity analysis of the basic designed lens, an optimization design is conducted to reduce the sensitivity for each tolerance. While maintaining the design performance of the basic optical system as it is or partially improving it, in order to reduce the tolerance sensitivity, factors that can have an effect are identified and optimized.

In Chapter B-1, the direction of the reduction design through material sensitivity analysis and the characteristics of the redesigned optical system are studied. In Chapters B-2 and B-3, the performance of the redesigned optical system is evaluated and the tolerance sensitivity results are analyzed. and compare with the results of the basic optical system. Chapter B-4 compares and evaluates the expected production yield using Monte Carlo simulation in Code-V for quantitative evaluation of tolerance sensitivity, and Chapter B-5 checks the amount of distortion change according to tolerance.

Lastly, in chapter B-6, in order to analyze the sensitivity according to the change in the refractive index of the material, the effect of the change in the refractive index on the sensitivity is analyzed by setting all materials in the EP series and virtual materials to verify data validity, performing optimization, and comparing them. do.

B-1. Optimally designed lens system analysis

20 is a diagram showing the MTF sensitivity to the refractive index of each material according to a preferred embodiment of the present invention, and FIG. 21 is a diagram showing the MTF sensitivity to the Abbe number of each material according to a preferred embodiment of the present invention. 22 is a view for explaining lens characteristics of the redesigned optical system according to a preferred embodiment of the present invention, and FIG. 23 is a view for explaining the layout of the redesigned optical system according to a preferred embodiment of the present invention. is a diagram for explaining the lens aspheric coefficient of the redesigned optical system according to a preferred embodiment of the present invention.

Based on the results obtained through the sensitivity analysis described in the previous chapter, the basic optical system is optimized. Design data analysis for lens group tilt and decenter and lens thickness, which had the greatest impact among the above sensitivities, is conducted. In the case of an optical system with a low F/#, such as the basic optical system, the angle of incidence increases while opening the falling light to ensure sufficient light quantity for the same TTL. As a result, the power of lens #1 increases and the sensitivity increases. Analyze the sensitivity to the refractive index and Abbe number of basic optical system materials.

As expected, as shown in FIG. 20, it can be seen that Lens #1 has the highest sensitivity, followed by lens #5. As a result of comparing the sensitivity to the Abbe number of each material, FIG. 21 shows a lower level of change than the sensitivity of the refractive index, and a relative MTF change of about 5% in lens #5 and lens #6 can be confirmed.

Before proceeding with optimization based on these results, in the case of lens #1 with high sensitivity, the variables were not greatly restricted because the changed elements had a great influence on the change in TTL of the entire optical system. Next, a material with a high refractive index of EP9000 was applied to the material of lens #5 with high sensitivity and lens #2 with relatively low sensitivity, respectively, and the change in sensitivity was confirmed while optimizing. It can be seen that the sensitivity is the lowest.

In addition, in order to equally distribute the power of lens #1 and lens #2, the thickness of each lens was adjusted and the value of the radius was limited. I also changed the curvature of surface #6 from negative (-) to positive (+). In addition, the design is carried out to reduce spherical aberration through bending that changes the radius of curvature of each lens surface with the same tendency.

If the conic constant has a large absolute value, a large calculation error may occur in the MTF, so design with restrictions on it. It can be confirmed that the absolute value of the radius of curvature is reduced in the basic design lens, and since the curvature of the surfaces constituting each lens changes with the same tendency, it can be confirmed that the tolerance sensitivity is reduced by setting the bending characteristics.

In addition, it is designed according to the power while adjusting the thickness of the lens. In addition, when comparing the shape of the basic design and the optimally designed lens, there is no significant difference from the basic optical system, but the sensitivity to tolerance is reduced through optimization with changes in each aspheric coefficient, thickness, and radius.

22 shows the characteristics of the optical system redesigned through optimization.

23 shows the layout of the redesigned optical system, and while optimizing, the y semi-aperture of surface #2 was 0.94 mm, the y semi-aperture of surface #6 was 0.71 mm, and the y semi-aperture of surface #8 was 0.97. Design with vignetting in mm.

As shown in FIG. 24, the aspheric coefficient of the redesigned optical system is set to the 14th order for surfaces #2 to #7, and additionally set to the 16th order for surfaces #8 to #9. And in the case of surfaces #10 to #13, the optimization design is performed by setting up to the 20th order of aspheric coefficients with Qcon aspheric surfaces.

B-2. Performance evaluation and analysis of optimized designed lens system

B-2-1. aberration analysis

25 is a diagram showing the results of aberration analysis of the redesigned optical system according to a preferred embodiment of the present invention.

25 for spherical aberration, astigmatism and distortion aberration, as mentioned in the previous chapter, spherical aberration has a smaller value than the basic optical system within 0.05mm, and the curvature difference between the astigmatism meridional curve and the sagittal curve is almost identical to that of the initial design. appear similar. In addition, it can be confirmed that the distortion aberration satisfies the design performance within 2%.

B-2-2. MTF (Modulation Transfer Function)

26 is a diagram showing MTF performance evaluation results for each field of the redesigned optical system according to a preferred embodiment of the present invention, and FIG. 27 is a diagram showing the MTF curve of the redesigned optical system according to a preferred embodiment of the present invention.

The MTF performance analysis results of the redesigned optical system are as follows. In the case of FIG. 26, a graph showing MTF performance for each field is confirmed at a similar level compared to the basic optical system.

The MTF change amount according to the image sensor position in FIG. 27 also shows a field curvature of 3 μm or less in all fields except for the 1.0 field.

B-2-3. Relative Illumination (RI)

28 is a diagram showing the result of analyzing the ambient light ratio of the redesigned optical system according to a preferred embodiment of the present invention.

The peripheral light ratio (RI) of the redesigned optical system is as shown in FIG. Here, 1.1F gives an extra margin of 0.1mm to the image height, so there is no effect on performance. In addition, the RI variation by field has a stable value within 10%.

B-3. Tolerance sensitivity analysis and comparison

FIG. 29 is a diagram showing MTF sensitivity to lens group decenter (DSY) of the redesigned optical system according to a preferred embodiment of the present invention, and FIG. 30 is a diagram showing the eccentricity of lens #1 according to a preferred embodiment of the present invention. 31 shows the MTF sensitivity to lens group tilt (BTY) of the redesigned optical system according to a preferred embodiment of the present invention. FIG. 32 is a diagram showing the MTF sensitivity to the displacement (DSZ) of the redesigned optical system according to a preferred embodiment of the present invention, and FIG. 33 is a diagram of the redesigned optical system according to a preferred embodiment of the present invention. 34 is a diagram showing the MTF sensitivity to the Zernike coefficient z8, and FIG. 34 is a diagram showing the MTF sensitivity to the Zernike coefficient z9 of the redesigned optical system according to a preferred embodiment of the present invention.

After optimization, the tolerance sensitivity of the redesigned optical system is analyzed. 29 to 34 show the results of additional analysis on lens group decenter, tilt, lens displacement, Zernike coefficient z8, and z9 spherical aberration, which were confirmed to have an MTF change of 30% or more among a total of seven types reviewed in the battlefield.

29 is the result of confirming the sensitivity with the MTF variation for each lens' eccentricity, and compared to the sensitivity of the basic optical system, it can be seen that the MTF variation decreases in the entire area. In particular, it is characteristic that the sensitivity of over 40% in lens #1 has decreased to within 30%.

Next, the sensitivity for the lens group decenter is compared with the basic optical system while checking the amount of change by applying a tolerance of 5um to lens #1 for the actual optical system. 30, it is confirmed that the MTF score of the line graph is about 5% higher in the redesigned optical system than the basic optical system in all fields except for the 0.3 field, and the amount of MTF change according to the tolerance of the bar graph is also low in all fields. .

It can be seen that the result of the lens group tilt in FIG. 31 is reduced compared to the maximum sensitivity of the basic optical system of 48%, and as a result of the displacement in FIG.

As shown in FIGS. 33 and 34, when comparing the MTF sensitivity to spherical aberration of the Zernike Sag z8 & z9 coefficient with the basic optical system, it can be confirmed that the MTF variation within 5% is slightly reduced in surfaces #1 and #5.

B-4. Monte Carlo simulation

35 is a diagram showing comparison results of Monte Carlo simulation for each field according to a preferred embodiment of the present invention, and FIG. 36 is a diagram showing Monte Carlo simulation results of a basic optical system and a redesigned optical system according to a preferred embodiment of the present invention.

In order to more quantitatively evaluate and compare the change in tolerance sensitivity identified above, the redesigned optical system is re-evaluated through Monte Carlo simulation.

Monte Carlo is a wide range of computer algorithms that use the method of iterative random sampling to obtain mathematical results. The essential idea of this algorithm is to use randomness to solve problems that may be deterministic. This method is usually used to solve physics or mathematical problems, and is mainly used in optimization, numerical integration, and derivation from probability distributions.

Code-V, a lens design program, also provides Monte Carlo simulation, and based on this, you can find out the MTF expected production yield for tolerance sensitivity. First, it is set to proceed in the transverse direction of the optical axis, and the frequency proceeds at Nyquist/4, 110lp/mm, and the number of simulations is performed at 1000 times.

35 shows the production yield of the basic optical system and the redesigned optical system based on the MTF of 30%, and the difference between the two optical systems can also be confirmed.

36 is a graph comparing expected production yield according to MTF for each field of a basic optical system and a redesigned optical system through Monte Carlo simulation. Here, the x-axis refers to the MTF value and the y-axis refers to the production yield. When evaluated based on the MTF of 30%, the expected production yield by field varies, but when evaluating the overall yield, the redesigned optical system shows a 7% improvement compared to the basic optical system.

B-5. Distortion analysis for tolerance sensitivity

37 is a diagram showing a distortion change amount with respect to tolerance sensitivity according to a preferred embodiment of the present invention.

In this chapter, the amount of distortion change per field according to tolerance sensitivity is analyzed. First of all, since the amount of distortion change according to each tolerance sensitivity cannot be directly obtained in Code-V, distortion by field is checked based on each optical system obtained through Monte Carlo simulation in the previous chapter, and the results of the basic optical system and the redesigned optical system are analyzed. do comparative analysis

100 random optical systems made in Monte Carlo simulation are made into a sequence, distortion is checked for each optical system, and the distribution of distortion for each field is shown as a box plot as shown in FIG. 37.

Compared to the basic optical system, the distortion change of the redesigned optical system is not very different, and the deviation within 0.3% can be confirmed. As the result confirmed in the previous chapter, it can be confirmed once again that the distortion value also increases as the field increases.

Based on the redesigned optical system, the results of the tolerance sensitivity were compared and analyzed, and it was confirmed that the tolerance sensitivity was reduced through the result of the decrease in MTF variation for tolerances such as eccentricity and tilt of the lens compared to the basic optical system, and a more quantitative evaluation. As a result of checking through Monte Carlo simulation, it was confirmed that the redesigned optical system is expected to improve the expected production yield by about 7% based on the MTF of 30%. In addition, it was confirmed that the size of the distribution has a deviation of less than 0.3% compared to the basic optical system in the result of sensitivity to distortion.

In the next chapter, other materials that can replace EP9000, a material with a high refractive index used in lens #5 of the redesigned optical system, are reviewed, and the tolerance sensitivity of various materials is also compared and analyzed, and the effect of the change in refractive index on the tolerance sensitivity is added. Find out with

B-6. Sensitivity analysis according to refractive index

38 is a diagram showing the refractive index and Monte Carlo simulation results for each EP material according to a preferred embodiment of the present invention, and FIG. 39 is a diagram showing the refractive index and expected production yield for each EP material according to a preferred embodiment of the present invention.

In this chapter, based on the results confirmed above, the effect of the refractive index change through material change on the tolerance sensitivity is compared and analyzed.

B-6-1. Characteristics of plastic materials

Plastic materials are characterized by light weight, high impact durability, more diverse configurations than glass, and low price. Most of the plastic materials are produced by injection molds. The manufacturing cost of molds is high, but it can be overcome by mass production. As the performance of the mobile optical system continues to improve and the pixel size of the sensor becomes smaller, the market demands light and inexpensive conditions that are more and more resistant to environmental durability. As a result, development of plastic materials is actively progressing.

Among plastic materials, the EP series material used in the redesigned optical system is a product produced by Mitsubishi gas chemical in Japan, and has excellent characteristics in terms of relatively high refractive index, transparency, and temperature resistance.

Here, the redesigned optical system for various materials with a refractive index of 1.6 or more is reinterpreted and optimized, and at this time, the change in tolerance sensitivity is confirmed and compared and analyzed through Monte Carlo simulation.

B-6-2. Sensitivity analysis according to material change

Among the various plastic materials identified above, by redesigning the optical system using a material with a different refractive index other than the EP9000 material used in the redesigned optical system, the change in tolerance sensitivity to the change in refractive index is compared through Monte Carlo simulation.

First, the EP9000 of lens #5 of the redesigned optical system is changed from EP5000 to EP8000 and optimized according to the design goal, and the result is compared between the basic optical system (EP4500) and the redesigned optical system (EP9000) through Monte Carlo simulation. In addition, by applying virtual materials EPSP1 to EPSP4, the change when a higher refractive index is applied is also analyzed.

38 is a result of confirming the sensitivity change according to the refractive index of each material in the EP series through Monte Carlo simulation.

The Monte Carlo simulation used here is the result of setting an MTF of 30% as a standard for each field and comparing the expected production yield by material at that time. Based on the EP4500 used for lens #5 of the basic optical system, it can be confirmed that the expected production yield increases while the tolerance sensitivity decreases as the EP-based material with a high refractive index is applied, and the difference in refractive index of each material is about 0.01.

39 is a graph showing the refractive index and expected production yield for each EP material, and it can be seen that the expected production yield increases while tolerance sensitivity decreases as a material with a high refractive index is used. In addition, it can be confirmed that the yield increases when EPSP1 to EPSP4 randomly generated as virtual materials are applied to confirm data validity, but there is also a possibility that the yield may decrease as the increasing slope becomes gentle.

C. theorem

As the demand for mobile optics rapidly increases, and as a result, higher performance is gradually achieved through continuous growth and technology development, tolerance sensitivity analysis is essential to reduce production costs while satisfying desired performance for lens design. In the present invention, in order to reduce the tolerance sensitivity of the mobile optical system, a reduction design is performed using a high refractive index material, and the change in the basic optical system is minimized according to the target design standard.

First, a 6P aspherical patented optical system was selected and optimized by fixing it to F-number 1.9 and EFL 3.5mm based on a 1/3-inch pixel size 1.12um sensor according to the design goal, resulting in MTF performance and field better than the existing patented optical system. An optical system with improved curvature and RI can be obtained, and this is set as the basic optical system according to the present invention.

As a result of the tolerance sensitivity analysis of the basic optical system, it was confirmed that the tolerance of tilt, decenter, surface sag, etc. was higher than the target MTF variation of 30%. Among them, the sensitivity to decenter, tilt, and displacement tolerances was relatively high, and in particular, lens #1 and surface #1 showed a relatively high level of sensitivity. In order to reduce this tolerance sensitivity, the present invention identifies the sensitivity of the refractive index and Abbe number of the material through sensitivity analysis of the plastic material, and as a result of comparing lens #5 with high sensitivity and lens #2 with low sensitivity, the most stable performance Reduction design was carried out by changing the material for lens #5, which has low sensitivity, and the EP4500 material of lens #5 was changed to the material of EP9000, which has a relatively high refractive index, and was redesigned to have MTF and aberration performance similar to the basic optical system. did When comparing the tolerance sensitivity of the redesigned optical system with the basic optical system, it was confirmed that the MTF change amount was improved in decenter, tilt, and Zernike Sag z8 & z9. Even when decenter was applied to the actual optical system, the MTF change amount and field curvature of the redesigned optical system improvement could be observed.

In order to more quantitatively confirm the effect of tolerance sensitivity, Monte Carlo simulation was used to compare expected production yields with all tolerances applied. I was able to confirm. In addition, as a result of examining the sensitivity to distortion, it was confirmed that the deviation of the redesigned optical system compared to the basic optical system had a value of less than 0.3%.

In addition, in order to confirm the correlation of the effect of materials with different refractive indices on tolerance sensitivity based on various materials, EP-type materials were applied to the redesigned optical system lens #5, respectively, and Monte Carlo simulation results according to tolerance sensitivity were compared. As a material with a high refractive index was used, it was confirmed that the expected production yield increased linearly while the sensitivity decreased.

In addition, it was confirmed that the results of applying randomly generated EPSP1 to EPSP4 as virtual materials for data validation showed that the yield increased, but the possibility of decreasing as the increasing slope became gentle appeared. Therefore, selecting a material with an appropriate refractive index is expected to contribute to reducing tolerance sensitivity and improving the performance of optical design.

Operations according to the present embodiments may be implemented in the form of program instructions that can be executed through various computer means and recorded in a computer readable storage medium. A computer readable storage medium refers to any medium that participates in providing instructions to a processor for execution. A computer readable storage medium may include program instructions, data files, data structures, or combinations thereof. For example, there may be a magnetic medium, an optical recording medium, a memory, and the like. The computer program may be distributed over networked computer systems so that computer readable codes are stored and executed in a distributed manner. Functional programs, codes, and code segments for implementing this embodiment may be easily inferred by programmers in the art to which this embodiment belongs.

These embodiments are for explaining the technical idea of this embodiment, and the scope of the technical idea of this embodiment is not limited by these embodiments. The scope of protection of this embodiment should be construed according to the claims below, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of rights of this embodiment.

100: design device,
110: processor,
130: computer readable storage medium,
131: program,
150: communication bus,
170: input/output interface,
190: communication interface

Claims (13)

Setting a basic optical system based on a 6P mobile optical system using a preset design target optical system;
Evaluating performance of the basic optical system;
analyzing tolerance sensitivity of the basic optical system;
Acquiring a redesigned optical system by redesigning the basic optical system by changing a material for at least one lens of the basic optical system based on a tolerance sensitivity analysis result for the basic optical system;
Evaluating performance of the redesigned optical system;
Analyzing tolerance sensitivity of the redesigned optical system and analyzing expected production yield and distortion change for the basic optical system and the redesigned optical system using Monte Carlo simulation; and
The redesigned optical system is redesigned using the tolerance sensitivity result according to the refractive index change of at least one lens of the redesigned optical system based on the analysis result of the tolerance sensitivity, expected production yield, and distortion change of the redesigned optical system. Acquiring an optical system;
A design method for reducing tolerance sensitivity of a 6P mobile optical system comprising a. In paragraph 1,
The design target optical system,
The pixel is 13.2M, the F/# is 1.9, the angle of view is 78 °, the EFL (Effective Focal Length) is 3.51mm, and the optical system includes 6 lenses,
A design method for reducing tolerance sensitivity of 6P mobile optics. In paragraph 2,
In the basic optical system performance evaluation step,
Based on the design target optical system, it consists of evaluating the performance of the basic optical system by performing aberration analysis, MTF (Modulation Transfer Function) performance evaluation, and Relative Illumination (RI) analysis,
The basic optical system tolerance sensitivity analysis step,
Consisting of analyzing the tolerance sensitivity of the basic optical system for shape sensitivity, unit sensitivity and assembly sensitivity,
A design method for reducing tolerance sensitivity of 6P mobile optics. In paragraph 3,
In the basic optical system performance evaluation step,
Performing aberration analysis on the basic optical system by analyzing aberrations including spherical aberration, astigmatism and distortion aberration, and analyzing MTF with a spatial frequency of 1101p/mm to evaluate MTF performance of the basic optical system, It consists of analyzing the ambient light ratio (RI) for the basic optical system by analyzing the ambient light ratio (RI) indicating the degree of darkness of the outer edge with respect to the center of the upper surface,
The basic optical system tolerance sensitivity analysis step,
By analyzing the sensitivity to Zernike Sag, the shape sensitivity of the basic optical system is analyzed, and the unit sensitivity of the basic optical system based on lens thickness, surface decenter, and surface tilt and analyzing the assembly sensitivity of the basic optical system based on lens decenter, lens tilt and axial displacement,
A design method for reducing tolerance sensitivity of 6P mobile optics. In paragraph 3,
The step of acquiring the redesigned optical system,
Analyzing the sensitivity to the refractive index and Abbe number of the material of the basic optical system, and changing the material for at least one lens of the basic optical system to a material having a high refractive index based on the analysis result of the sensitivity to the refractive index and Abbe number of the material Consisting of redesigning the basic optical system,
A design method for reducing tolerance sensitivity of 6P mobile optics. In paragraph 5,
In the performance evaluation step of the redesigned optical system,
It consists of evaluating the performance of the redesigned optical system by performing aberration analysis, MTF performance evaluation, and ambient light ratio (RI) analysis,
The redesign optical system tolerance sensitivity analysis step,
Based on the tolerance sensitivity analysis result for the basic optical system, the tolerance sensitivity of the redesigned optical system is analyzed for the tolerance identified as MTF variation of 30% or more, and set to proceed in the transverse direction of the optical axis, and the spatial frequency is set to 1101p/mm The expected production yield for each of the basic optical system and the redesigned optical system is analyzed based on the MTF of 30% using Monte Carlo simulation, and the distortion change for each of the basic optical system and the redesigned optical system is analyzed using Monte Carlo simulation. consisting of doing
A design method for reducing tolerance sensitivity of 6P mobile optics. In paragraph 6,
The final optical system acquisition step,
A material having a different refractive index is applied to at least one lens of the redesigned optical system, and a change in tolerance sensitivity to a change in refractive index is compared using a Monte Carlo simulation, and at least one lens of the redesigned optical system is selected based on the comparison result. Consisting of changing to this high material to obtain the final optical system,
A design method for reducing tolerance sensitivity of 6P mobile optics. In paragraph 7,
The final optical system acquisition step,
Using Monte Carlo simulation, based on MTF of 30%, the expected production yield for each of the plurality of redesigned optical systems to which a plurality of materials having different refractive indices from the basic optical system are applied, respectively, and a change in tolerance sensitivity according to a change in refractive index are compared. made up,
A design method for reducing tolerance sensitivity of 6P mobile optics. A computer program stored in a computer readable storage medium to execute the design method for reducing tolerance sensitivity of a 6P mobile optical system according to any one of claims 1 to 8 in a computer. As a design device that performs a design for reducing tolerance sensitivity of a 6P mobile optical system,
a memory for storing one or more programs for performing a design for reducing tolerance sensitivity of a 6P mobile optical system; and
one or more processors performing an operation for performing a design for tolerance sensitivity reduction of a 6P mobile optical system according to the one or more programs stored in the memory;
Including,
the processor,
Set up a basic optical system based on a 6P mobile optical system using a preset design target optical system,
Evaluate the performance of the basic optical system,
Analyzing tolerance sensitivity of the basic optical system;
Obtaining a redesigned optical system by redesigning the basic optical system by changing a material for at least one lens of the basic optical system based on a tolerance sensitivity analysis result for the basic optical system;
Evaluate the performance of the redesigned optical system,
Analyzing tolerance sensitivity of the redesigned optical system, analyzing expected production yield and distortion change for the basic optical system and the redesigned optical system using Monte Carlo simulation,
The redesigned optical system is redesigned using the tolerance sensitivity result according to the refractive index change of at least one lens of the redesigned optical system based on the analysis result of the tolerance sensitivity, expected production yield, and distortion change of the redesigned optical system. Acquiring optics,
A design device for reducing tolerance sensitivity of 6P mobile optics. In paragraph 10,
The design target optical system,
The pixel is 13.2M, the F/# is 1.9, the angle of view is 78 °, the EFL (Effective Focal Length) is 3.51mm, and the optical system includes 6 lenses,
A design device for reducing tolerance sensitivity of 6P mobile optics. In paragraph 11,
the processor,
Based on the design target optical system, aberration analysis, MTF (Modulation Transfer Function) performance evaluation, and relative illumination (RI) analysis are performed to evaluate the performance of the basic optical system,
Analyzing the tolerance sensitivity of the basic optical system for shape sensitivity, unit sensitivity and assembly sensitivity,
A design device for reducing tolerance sensitivity of 6P mobile optics. In paragraph 12,
the processor,
Performing aberration analysis on the basic optical system by analyzing aberrations including spherical aberration, astigmatism and distortion aberration, and analyzing MTF with a spatial frequency of 1101p/mm to evaluate MTF performance of the basic optical system, By analyzing the ambient light ratio (RI) indicating the degree of darkness of the outer edge of the center of the upper surface, performing the peripheral light ratio (RI) analysis on the basic optical system,
By analyzing the sensitivity to Zernike Sag, the shape sensitivity of the basic optical system is analyzed, and the unit sensitivity of the basic optical system based on lens thickness, surface decenter, and surface tilt Analyzing the assembly sensitivity of the basic optical system based on lens decenter, lens tilt and axial displacement,
A design device for reducing tolerance sensitivity of 6P mobile optics.

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