CN115343024A - Lens optical effective diameter internal stress analysis method - Google Patents

Lens optical effective diameter internal stress analysis method Download PDF

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CN115343024A
CN115343024A CN202210905517.XA CN202210905517A CN115343024A CN 115343024 A CN115343024 A CN 115343024A CN 202210905517 A CN202210905517 A CN 202210905517A CN 115343024 A CN115343024 A CN 115343024A
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lens
stress
image
effective diameter
circle
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张丁增
李长明
郭崇波
李亮
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Jiangxi Lianyi Optics Co Ltd
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    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/08—Testing mechanical properties
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Abstract

The invention relates to the technical field of lens detection, in particular to an internal stress analysis method for an optical effective diameter of a lens, which comprises the following steps: measuring the actual outer diameter of the lens and the actual optical effective diameter of the lens; measuring the internal stress of the lens through a stress meter to obtain a measurement area image covering the actual lens; finding all boundary points of the boundary stress value to obtain a boundary point set; obtaining the outer diameter of the lens in the image of the measuring area; and solving the effective diameter of the lens in the image of the measuring area so as to carry out data analysis on the internal stress in the effective diameter of the lens. The method comprises the steps of placing a lens on a stress instrument carrier, detecting stress, and storing pixel point data of a measurement area image; the method comprises the steps of fitting a circle by a least square method on data in an image to obtain the outer diameter of the lens under an image coordinate system, and deducing the size of the optical effective diameter under the image coordinate system.

Description

Lens optical effective diameter internal stress analysis method
Technical Field
The invention relates to the technical field of lens detection, in particular to an internal stress analysis method for an optical effective diameter of a lens.
Background
Optical lenses are one of the key components of precision optical instruments. In the process of installing the optical lens, glue or screws are often used for installing and fixing the optical lens in the radial direction, assembling forces such as glue force, screw pre-tightening force and the like can form radial loads of the optical lens, and unevenly distributed stress is caused in the optical lens, so that the imaging accuracy of an optical system is influenced.
The invention with the application number of CN202110016131.9 provides a radial loading device for testing the stress of an optical lens, and radial quantitative loading tests with different load sizes and quantities can be carried out on the optical lens. The device comprises a bottom plate, a lens supporting platform, a force application system and a force measurement system. The lens supporting platform and the force application system are fixed on the bottom plate through connecting pieces, the force measurement system is connected with the bottom plate through a movable connecting piece, and the movable connecting piece can move along the radial direction of the lens; the screw compression spring in the force application system generates force, and the sensor of the measuring system measures the force, so that the precise control of the radial load size and direction is realized. The invention realizes the radial quantitative loading of the optical lens, has high loading precision in the loading direction and large adjustment range of the number and the size of the load, and is suitable for the radial loading of the optical lenses with various sizes. The invention can be widely applied to the research of the stress distribution state of the high-precision optical element and the quantitative mapping relation between the assembly force and the internal stress state of the optical element.
The above patent can detect the stress distribution state of the lens, but the current stress meter can detect the internal stress of the lens and output the maximum value, the average value and the minimum value of the internal stress in a specific range, but the limitation is that the selected specific range can only be selected by a man-made subjective frame, when analyzing the stress of the lens in the optical effective diameter and the distribution condition, the maximum value, the average value and the minimum value of the internal stress in the optical effective diameter can not be accurately output,
disclosure of Invention
The present invention is directed to at least one of the problems of the prior art, and provides a method for analyzing stress in an optical effective diameter of a lens.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows: an analysis method for internal stress of an optical effective diameter of a lens comprises the following steps:
step 1, measuring the actual outer diameter of the lens and the actual optical effective diameter of the lens;
step 2, measuring the internal stress of the lens through a stress meter to obtain a measurement area image covering the actual lens, wherein the measurement area image and the actual lens are in a size scaling relationship, pixel point data of the measurement area image are stored, and one pixel point corresponds to one stress numerical value;
step 3, setting and distinguishing boundary stress values of the lens and the measuring background according to experimental conditions, and finding all boundary points of the boundary stress values in the measuring area image to obtain a boundary point set;
step 4, fitting a circle on the boundary point set by a least square method to obtain the outer diameter of the lens in the image of the measurement area;
step 5, according to the size scaling relationship between the lens image in the measurement area image and the actual lens, the formula is as follows: and (3) calculating the effective diameter of the lens in the image of the measurement area so as to analyze the internal stress in the effective diameter of the lens.
Furthermore, the stress gauge adopts a birefringence stress gauge, and the optical path difference is used for representing the stress.
Further, before the internal stress of the lens is measured by the stress gauge, the stress gauge carrying platform is cleaned and decontaminated by using an organic solvent.
Further, the boundary stress value is greater than 4nm.
Further, in step 3, the measurement region image is divided into a left half and a right half, and boundary points are respectively obtained for the left half and the right half of the measurement region image.
Further, the step 4 specifically includes:
according to the centre of a circle (A, B) and radius R can define a circle on the plane, and the general formula of the equation of the circle on the plane is x 2 +y 2 + ax + by + c =0, is a linear equation for a, b and c;
the circle centers (A, B) and the radius R are shown as the following equation set (1):
Figure BDA0003772320640000031
establishing a mathematical model of circle fitting by using a least square method, solving the values of the parameters a, B and c, and then solving the actual parameters A, B and R of the circle according to an equation set;
a mathematical model of the circle fit is created using the least squares method as follows:
obtaining N (N is more than or equal to 3) group data (x) of the boundary point set i ，y i ) (i =1,2,3, \8230;, N) requires an objective function according to the general formula and the principle of least squares
Figure BDA0003772320640000032
The F (a, b, c) is used to calculate the partial derivatives of a, b, c, and the partial derivatives are made equal to zero, so as to obtain the extreme points, which are as follows: order to
Figure BDA0003772320640000033
Namely:
Figure BDA0003772320640000034
setting:
Figure BDA0003772320640000035
Figure BDA0003772320640000036
then:
Figure BDA0003772320640000037
solving the above equation can obtain a, b, c:
Figure BDA0003772320640000038
wherein:
Figure BDA0003772320640000041
and then the center and the radius of the outer diameter of the lens in the image can be obtained by the equation set (1).
Further, after fitting a circle to the boundary point set by a least square method, median filtering is performed on the full-lens area in the image.
Further, the median filtering process is detailed as follows:
setting m rows and k columns of pixel points of the image of the measurement area, and performing the following operations on pixel point data: taking the 3x3 neighborhood of the ith row and the jth column (2 < = i < = m-1,2< = j < = k-1) for example, sorting the 9 data in the neighborhood from small to large, and taking the median of the 9 data to represent the data of the ith row and the jth column.
The invention has the beneficial effects that: as can be seen from the above description of the present invention, compared with the prior art, the method for analyzing the internal stress of the optical effective diameter of the lens of the present invention comprises placing the lens on a stress meter carrying platform for alcohol decontamination, detecting the stress, and storing pixel data of the image of the measurement area; the invention carries out area identification according to the structural data of the lens, carries out internal stress data analysis in the optical effective diameter, and avoids artificial measurement errors caused by artificial selection of areas; meanwhile, a median filtering process is introduced, so that the influence of dirt on the maximum value of the internal stress is reduced.
Drawings
FIG. 1 is a flowchart illustrating the steps of a stress analysis method for an optical effective diameter of a lens according to a preferred embodiment of the present invention;
fig. 2 is a schematic structural diagram of a measurement region image in the preferred embodiment of the present invention.
Detailed Description
The technical solutions in the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments.
In the description of the present invention, it should be noted that, unless explicitly stated or limited otherwise, the terms "connected" and "connected" are to be interpreted broadly, e.g., as being fixed or detachable or integrally connected; can be mechanically or electrically connected; may be directly connected or indirectly connected through an intermediate. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Referring to fig. 1, a preferred embodiment of the present invention, a method for stress analysis in an optical effective diameter of a lens, comprises the following steps:
step 1, measuring the actual outer diameter of the lens and the actual optical effective diameter of the lens;
step 2, measuring the internal stress of the lens through a stress meter to obtain a measurement area image covering the actual lens, wherein the measurement area image and the actual lens are in a size scaling relationship, pixel point data of the measurement area image are stored, and one pixel point corresponds to one stress value;
step 3, setting and distinguishing boundary stress values of the lens and the measuring background according to experimental conditions, and finding all boundary points of the boundary stress values in the measuring area image to obtain a boundary point set;
step 4, fitting a circle on the boundary point set by a least square method to obtain the outer diameter of the lens in the image of the measurement area;
step 5, according to the size scaling relationship between the lens image in the measurement area image and the actual lens, the formula is as follows: and (3) solving the effective diameter of the lens in the image of the measurement area so as to perform data analysis on internal stress in the effective diameter of the lens.
Referring to fig. 2, the lens is placed on the measurement background, the image of the measurement area is a square image, each pixel point corresponds to a stress value, the lens includes an optical effective area of the lens and a non-optical effective area of the lens in the image, the outer diameter of the optical effective area of the lens is the effective diameter of the lens in the image, the outer diameter of the non-optical effective area of the lens is the outer diameter of the lens in the image, and the set of boundary points is the junction of the measurement background and the non-optical effective area of the lens.
The method for analyzing the internal stress of the optical effective diameter of the lens comprises the steps of placing the lens on a stress instrument carrying platform for alcohol decontamination, detecting the stress, and storing pixel point data of an image of a measurement area; the invention carries out area identification according to the structural data of the lens, carries out internal stress data analysis in the optical effective diameter, and avoids artificial measurement errors caused by artificial selection of areas; meanwhile, a median filtering process is introduced, so that the influence of dirt on the maximum value of the internal stress is reduced.
As a preferred embodiment of the present invention, it may also have the following additional technical features:
in this embodiment, the stress gauge is a birefringence stress gauge, and the optical path difference is used to represent the stress. Specifically, the stress gauge is a Shanghai Zongqing Photonic stress birefringence gauge, model WPA-200, and the unit of the stress is nm.
In this embodiment, before the internal stress of the lens is measured by the stress gauge, the stress gauge stage is cleaned and decontaminated using an organic solvent. Cleaning and decontamination treatment is carried out before measurement, so that the measurement result is prevented from being influenced by stains, and the organic solvent can adopt alcohol.
In this embodiment, the boundary stress value is greater than 4nm. Experiments verify that the stress value of the measuring background is between 0 and 3nm, and the stress value of the lens is greater than 4nm, so that the boundary stress value for distinguishing the lens from the measuring background is greater than 4nm.
In this embodiment, in step 3, the measurement region image is divided into a left half and a right half, and boundary points are respectively found for the left half and the right half of the measurement region image. Dividing the image of the measurement area into a left half side and a right half side, searching from the left side and the right side to the middle respectively, finding out a point with a first stress value larger than 4nmd on the left side and the right side as a boundary point on the left side and the right side, and finally forming a boundary point set by all the boundary points on the left side and the right side.
In this embodiment, the step 4 specifically includes:
according to the centre of a circle (A, B) and radius R can define a circle on the plane, and the general formula of the equation of the circle on the plane is x 2 +y 2 + ax + by + c =0, is a linear equation for a, b and c;
the circle centers (A, B) and the radius R are shown as the following equation set (1):
Figure BDA0003772320640000071
establishing a mathematical model of circle fitting by using a least square method, solving the values of the parameters a, B and c, and then solving the actual parameters A, B and R of the circle according to an equation set;
a mathematical model of the circle fit is created using the least squares method as follows:
obtaining N (N is more than or equal to 3) group data (x) of the boundary point set i ，y i ) (i =1,2,3, \8230;, N) requires an objective function according to the general formula and the principle of least squares
Figure BDA0003772320640000072
F (a, b, c) is used to calculate the partial derivatives of a, b, c, and the partial derivatives are made equal to zero, so as to obtain the extreme points, which are as follows: order to
Figure BDA0003772320640000073
Namely:
Figure BDA0003772320640000074
setting:
Figure BDA0003772320640000075
Figure BDA0003772320640000076
then:
Figure BDA0003772320640000077
solving the above equation can obtain a, b, c:
Figure BDA0003772320640000078
wherein:
Figure BDA0003772320640000081
and then the center and the radius of the outer diameter of the lens in the image can be obtained by the equation set (1).
In this embodiment, after fitting a circle to the set of boundary points by the least square method, median filtering is performed on the full-lens area in the image, and the detailed process of the median filtering is as follows:
setting m rows and k columns of pixel points of the image of the measurement area, and performing the following operations on pixel point data: taking the ith row and the jth column as an example (2 < = i < = m-1,2< = j < = k-1), taking a 3x3 neighborhood, sorting 9 data in the neighborhood from small to large, and taking the median of the 9 data to represent the data of the ith row and the jth column. The effect of removing low-frequency noise can be achieved through median filtering, meanwhile, the authenticity of data is kept, and the influence of dirt on the maximum value of the internal stress is reduced.
The above additional technical features can be freely combined and used in addition by those skilled in the art without conflict.
It is to be understood that the present invention has been described with reference to certain embodiments, and that various changes in the features and embodiments, or equivalent substitutions may be made therein by those skilled in the art without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims (8)

1. An analysis method for internal stress of an optical effective diameter of a lens is characterized by comprising the following steps:
step 1, measuring the actual outer diameter of the lens and the actual optical effective diameter of the lens;
step 2, measuring the internal stress of the lens through a stress meter to obtain a measurement area image covering the actual lens, wherein the measurement area image and the actual lens are in a size scaling relationship, pixel point data of the measurement area image are stored, and one pixel point corresponds to one stress value;
step 3, setting and distinguishing boundary stress values of the lens and the measuring background according to experimental conditions, and finding all boundary points of the boundary stress values in the measuring area image to obtain a boundary point set;
step 4, fitting a circle to the boundary point set by a least square method to obtain the outer diameter of the lens in the image of the measurement area;
step 5, according to the size scaling relationship between the lens image in the measurement area image and the actual lens, the formula is as follows: and (3) solving the effective diameter of the lens in the image of the measurement area so as to perform data analysis on internal stress in the effective diameter of the lens.
2. The stress analysis method of claim 1, wherein the stress gauge is a birefringence stress gauge, and the optical path difference is used to represent the stress.
3. The method for analyzing the internal stress of the optical effective diameter of the lens as claimed in claim 1, wherein the stress gauge stage is cleaned and decontaminated by an organic solvent before the internal stress of the lens is measured by the stress gauge.
4. The method for stress analysis within the optical effective diameter of a lens according to claim 1, wherein the boundary stress value is greater than 4nm.
5. The lens inner stress analysis method as claimed in claim 1, wherein in step 3, the measurement area image is divided into a left half and a right half, and the boundary points are respectively determined for the left half and the right half of the measurement area image.
6. The method for analyzing stress in an optical effective diameter of a lens according to claim 1, wherein the step 4 specifically comprises:
according to the centre of a circle (A, B) and radius R can define a circle on the plane, and the general formula of the equation of the circle on the plane is x 2 +y 2 + ax + by + c =0, which is a linear equation for a, b and c;
the circle centers (A, B) and the radius R are shown as the following equation set (1):
Figure FDA0003772320630000021
establishing a mathematical model of circle fitting by using a least square method, solving the values of the parameters a, B and c, and then solving the actual parameters A, B and R of the circle according to an equation set;
a mathematical model of the circle fit is created using the least squares method as follows:
in obtainingN (N is more than or equal to 3) groups of data (x) of the boundary point set i ，y i ) (i =1,2,3, \8230;, N) requires an objective function according to the general formula and the principle of least squares
Figure FDA0003772320630000022
The F (a, b, c) is used to calculate the partial derivatives of a, b, c, and the partial derivatives are made equal to zero, so as to obtain the extreme points, which are as follows: order to
Figure FDA0003772320630000023
Namely:
Figure FDA0003772320630000024
setting:
Figure FDA0003772320630000025
Figure FDA0003772320630000026
then:
Figure FDA0003772320630000027
solving the above equation can obtain a, b, c:
Figure FDA0003772320630000031
wherein:
Figure FDA0003772320630000032
and then the center and the radius of the outer diameter of the lens in the image can be obtained by the equation set (1).
7. The method for stress analysis in the optical effective diameter of the lens according to claim 1, wherein after fitting a circle to the set of boundary points by the least square method, the median filtering is performed on the full lens area in the image.
8. The lens optical effective diameter stress analysis method as claimed in claim 7, wherein the detailed process of the median filtering is as follows:
setting m rows and k columns of pixel points of the image of the measurement area, and performing the following operations on pixel point data: taking the ith row and the jth column as an example (2 < = i < = m-1,2< = j < = k-1), taking a 3x3 neighborhood, sorting 9 data in the neighborhood from small to large, and taking the median of the 9 data to represent the data of the ith row and the jth column.
CN202210905517.XA 2022-07-29 2022-07-29 Lens optical effective diameter internal stress analysis method Pending CN115343024A (en)

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