阅读说明：本技术 一种光学系统中消一次杂散光遮光罩的结构设计方法 (Structural design method of one-time stray light shading cover in optical system ) 是由 王玮鹭 王维 于 2020-12-29 设计创作，主要内容包括：一种光学系统中消一次杂散光遮光罩的结构设计方法,涉及光学系统设计技术领域,解决现有挡光环的设计存在光学系统重量增加,装配难度高,且无法满足光学系统消一次入射杂散光抑制要求的问题,设定入口处光学孔径的半径值,遮光罩半孔径,挡光环之间的轴向间距,挡光环的总数量,遮光罩总长,遮光罩的杂光抑制角以及光学系统视场角；在确定杂光抑制角后,对遮光罩半孔径,挡光环之间的轴向间距进行矩阵式离散采样；确定光线入射的位置范围；计算获得满足条件的交点的取值范围；记录该入射角度下不能满足条件的光线数目；实现消杂散光设计。本发明计算出来的遮光罩结构具有等高度等间距挡光环,解决工程应用中遮光罩结构复杂难加工难装配的问题。(A structural design method of a first-order stray light shielding cover in an optical system relates to the technical field of optical system design, solves the problems that the weight of the optical system is increased, the assembly difficulty is high, and the first-order incident stray light suppression requirement of the optical system cannot be met in the existing light shielding ring design, and sets the radius value of the optical aperture at an inlet, the half aperture of the light shielding cover, the axial distance between the light shielding rings, the total number of the light shielding rings, the total length of the light shielding cover, the stray light suppression angle of the light shielding cover and the field angle of the optical system; after the parasitic light suppression angle is determined, matrix discrete sampling is carried out on the half aperture of the light shield and the axial distance between light blocking rings; determining the position range of the incident light; calculating to obtain the value range of the intersection points meeting the conditions; recording the number of rays which cannot meet the conditions under the incident angle; the design of eliminating stray light is realized. The calculated light shield structure has light blocking rings with equal height and equal spacing, and the problem that the light shield structure is complex, difficult to process and difficult to assemble in engineering application is solved.)

1. A structural design method of a first-order stray light shading cover in an optical system is characterized by comprising the following steps: the method is realized by the following steps:

step one, setting a as the radius value of the optical aperture at the inlet, a⁺The total length of the light shield is Md; theta₀Is the stray light suppression angle of the lens hood, omega is the field angle of the optical system, and the stray light suppression angle theta of the lens hood₀The field angle omega of the optical system is positive, and d is negative;

in determining veiling glareAngle theta₀Then, a is given according to engineering experience⁺And d and a⁺D, carrying out matrix discrete sampling;

setting the included angle between the edge position light ray and the X axis not more than the stray light inhibition angle theta₀I.e. by

After finishing to obtain

For each group a in the step one⁺D, calculating corresponding M according to the numerical value obtained by discrete sampling to obtain an M matrix;

step three, taking an incident ray direction, recording the incident ray direction as theta, and determining the position range of the incident ray; setting the equation of the incident light as:

y＝tanθ(x+b)

b is the intersection point position of the incident ray and the X axis, and then the ray entering the inner part of the lens hood should satisfy:

intersection x of y-tan θ (x + b) and y-tan ω · x + a₁Not less than Md and

intersection x of y-tan θ (x + b) and y-tan ω · x-a₂≤Md；

For each group a in the step one⁺And d is a value of θ₀Within the range of 89 degrees, taking a value every 1 degree, and calculating to obtain the value range of the intersection point b meeting the condition;

step four, in the determined value range of b, setting y to tan theta (x + b) and y to tan omega x + a⁺Has an intersection of (x)₀,y₀) The intersection of y ═ tan θ (x + b) and y ═ tan ω · x + a is (x ═ tan ω · x + a)₀′,y₀′)；x₀Between (M +1) d and Md;

if x₀' not between (M +1) d and Md, the incident ray has an intersection with the light-barrier ring, i.e. the ray first strikes the light-barrier ring, whichThe light automatically meets the condition of eliminating primary scattering;

if x₀Between (M +1) d and Md, then there is no intersection point between the incident ray and the light-blocking ring, i.e. the ray first hits the cylinder wall, then the mathematical expression of the condition of primary scattering cancellation is:

(x₀,y₀) And (0, -a)⁺) Is connected to x_mIntersection point (x) of Md_m,y_m) Within the light-blocking ring, i.e. y_m≥a-Md tanω；

Calculating the satisfaction condition of the conditions in the step three, and recording the number of the light rays which cannot meet the conditions in the step three under the incident angle;

step five, for each group a⁺And d, superposing the number of the light rays which do not meet the conditions in the third step under all the angles to obtain the total number of the light rays which do not meet the conditions in the third step;

step six, storing the total number of the rays which do not meet the condition as and a⁺And d, when the matrix element is zero, the group a⁺And d is a value which satisfies the design of eliminating the stray light.

2. The method as claimed in claim 1, wherein the design of the first-order stray light shielding structure in the optical system comprises: according to a obtained in the sixth step⁺And d, calculating the value range of M, selecting the corresponding length of the light shield, finally obtaining the dimensions of the outer contour and the inner light blocking ring of the conical light shield, and finishing the structural design of the stray light eliminating light shield.

3. The method as claimed in claim 1, wherein the design of the first-order stray light shielding structure in the optical system comprises: the outer contour of the light shield is designed into a conical barrel which is consistent with the envelope divergence angle of marginal field ray.

Technical Field

The invention relates to the technical field of optical system design, in particular to a structural design method of a first-order stray light shading cover in an optical system.

Background

In an optical system, stray light generally refers to non-imaging light reaching the image plane of the optical system, and corresponds to "noise" of the optical system. The influence of the star image point on the camera is very obvious, so that the contrast of an image surface is greatly reduced, and the definition is deteriorated; the noise caused by stray light radiation may even overwhelm the target signal. Therefore, the stray light suppression design is one of the key technologies of the imaging camera, and a method of designing a light shield for the camera to suppress the influence of the stray light is often adopted.

The design of the light shield is divided into a shape design and a light blocking ring design, and the existence of the light blocking ring can effectively reduce the incidence of stray light with a smaller off-axis angle. The lens hood appearance has cylindric and taper two kinds, and the arrangement of light barrier ring also has two kinds: the light blocking rings are arranged at the same height and the light blocking rings are arranged in a gradient manner. No matter which arrangement form of the light shield and the light blocking ring is adopted, the central idea is that incident first-level scattered stray light larger than a stray light inhibition angle is not directly irradiated on the primary mirror, and the arrangement of the light blocking ring is ensured not to block light rays within a visual field angle.

In previous researches, it is found that the light blocking rings are distributed more densely and better, but the number of the light blocking rings in practical engineering also increases the self weight of the optical system and increases the assembly difficulty, so that the number of the light blocking rings needs to be reduced by a proper amount. The height of the light blocking ring is increased to increase the reflection times of the stray light in the light blocking ring, and the times and the distribution of the light blocking ring have a certain relationship. Under the condition of considering the processing and adjusting difficulty, certain requirements are required on the number and the height of the light blocking rings, so that the light machine is convenient to adjust, and the requirement of an optical system for eliminating the primary incident stray light can be met.

In the current design, the light blocking rings are all equal in height or equal in spacing, and in order to facilitate engineering, a new calculation idea is provided for the design vacancy of the light blocking and shading cover structure with equal spacing and equal height. The design method of the invention is applied to engineering projects, can effectively simplify the production flow and the assembly flow of the light shield and the light blocking ring, reduce the processing cost and shorten the engineering period.

Disclosure of Invention

The invention provides a structural design method of a first-order stray light eliminating shade in an optical system, aiming at solving the problems that the weight of the optical system is increased, the assembly difficulty is high and the requirement of the optical system for eliminating the first-order incident stray light inhibition cannot be met in the design of the existing light blocking ring.

A structural design method for eliminating a stray light hood in an optical system is realized by the following steps:

step one, setting a as the radius value of the optical aperture at the inlet, a⁺The total length of the light shield is Md; theta₀Is the stray light suppression angle of the lens hood, omega is the field angle of the optical system, and the stray light suppression angle theta of the lens hood₀The field angle omega of the optical system is positive, and d is negative;

at a determined parasitic light suppression angle theta₀Then, a is given according to engineering experience⁺And d and a⁺D, carrying out matrix discrete sampling;

setting the included angle between the edge position light ray and the X axis to be less than or equal to the stray light inhibition angle theta₀I.e. by

After finishing to obtain

For each group a in the step one⁺D, calculating corresponding M according to the numerical value obtained by discrete sampling to obtain an M matrix;

step three, taking an incident ray direction, recording the incident ray direction as theta, and determining the position range of the incident ray; setting the equation of the incident light as:

y＝tanθ(x+b)

b is the intersection point position of the incident ray and the X axis, and then the ray entering the inner part of the lens hood should satisfy:

intersection x of y-tan θ (x + b) and y-tan ω · x + a₁Not less than Md and

intersection x of y-tan θ (x + b) and y-tan ω · x-a₂≤Md；

For each group a in the step one⁺And the value of dLet theta be at theta₀Within the range of 89 degrees, taking a value every 1 degree, and calculating to obtain the value range of the intersection point b meeting the condition;

step four, in the determined value range of b, setting y to tan theta (x + b) and y to tan omega x + a⁺Has an intersection of (x)₀,y₀) The intersection of y ═ tan θ (x + b) and y ═ tan ω · x + a is (x ═ tan ω · x + a)₀′,y₀′)；x₀Between (M +1) d and Md;

if x₀If the light ray is not between (M +1) d and Md, the incident light ray and the light-blocking ring have an intersection point, namely the light ray firstly irradiates the light-blocking ring, and the light ray automatically meets the condition of primary scattering elimination;

if x₀Between (M +1) d and Md, then there is no intersection point between the incident ray and the light-blocking ring, i.e. the ray first hits the cylinder wall, then the mathematical expression of the condition of primary scattering cancellation is:

(x₀,y₀) And (0, -a)⁺) Is connected to x_mIntersection point (x) of Md_m,y_m) Within the light-blocking ring, i.e. y_m≥a-Md tanω；

Calculating the satisfaction condition of the conditions in the step three, and recording the number of the light rays which cannot meet the conditions in the step three under the incident angle;

step five, for each group a⁺D, superposing the number of the light rays which do not meet the condition in the third step under all the angles to obtain the total number of the light rays which do not meet the condition in the third step;

step six, storing the total number of the rays which do not meet the condition in the step five as and a⁺And d, when the matrix is a zero matrix, the group a⁺And d satisfies the design requirement of eliminating the stray light once.

The invention has the beneficial effects that: according to the design method of the light shield for eliminating the primary scattering stray light, the light shield structure calculated by using a programming method has light blocking rings with equal height and equal spacing, and the problem that the light shield structure is complex, difficult to process and difficult to assemble in engineering application can be solved.

The invention aims to obtain light blocking rings with equal spacing and equal height through programmed calculation, and simultaneously meet the requirement of primary scattering elimination beyond a specific angle, so that the outer contour of the light shield is designed into a conical barrel consistent with the light enveloping divergence angle of the marginal field of view, and light is scattered at least twice through a structure before reaching the bottom plane of the light shield.

Drawings

Fig. 1 is a schematic structural coordinate diagram of an all-first stray light shielding cover in an optical system according to the present invention.

Detailed Description

The embodiment is described with reference to fig. 1, and a method for calculating a cone-shaped light shield structure of a light blocking ring with equal spacing and equal height is implemented by the following specific steps:

step one, setting the radius value of the optical aperture at the inlet as a and the radius value of the lens hood as a⁺The axial distance between the light blocking rings is d, the total number of the light blocking rings is M, namely the total length of the light shield is Md. Theta₀Is the stray light suppression angle of the lens hood, and ω is the angle of view of the optical system, where θ is the amount of angle₀And ω are both positive numbers and d is a negative number.

The variable to be optimized is a⁺，d，M。

By adopting the general idea of discrete ergodic sampling to determine the parasitic light suppression angle theta₀Then, a is given according to engineering experience⁺And d, carrying out matrix discrete sampling in the value ranges of the d and the d.

Step two, theta₀The light rays incident at angles above cannot reach the bottom surface directly. Here, in order to leave a margin, the edge of the light passing position is not taken, but the edge of the bottom surface outer cylinder is taken. This condition primarily limits the relationship between the overall length and the outer diameter of the light shield. The mathematical relationship is such that the included angle between the edge position light rays (the line connecting the top vertex and the bottom opposite vertex of the shade) and the X-axis shown in FIG. 1 is not greater than the parasitic light suppression angle θ₀I.e. by

After finishing to obtain

For each group a in the step one⁺And d, calculating corresponding M to obtain an M matrix.

And step three, meeting the condition of eliminating primary scattering can be divided into two cases, namely, if the incident light firstly reaches the outer side of the light blocking ring, the light can reach the bottom surface only after being scattered twice. The second situation is that if the incident light first reaches the cylinder wall of the light shield, the incident light needs to be shielded by the light blocking ring.

In order to ensure that the light rays at all angles and all positions can meet the condition of eliminating primary scattering, firstly, an incident light ray direction is taken and recorded as theta, and the position range of the incident light ray is determined. Let the equation of the incident ray be

y＝tanθ(x+b)

b is the intersection position of the ray with the X-axis.

Then the light rays striking the inside of the light shield should satisfy:

intersection x of y-tan θ (x + b) and y-tan ω · x + a₁Not less than Md and

intersection x of y-tan θ (x + b) and y-tan ω · x-a₂≤Md

For each group a in the step one⁺And d is a value of θ₀And in the range of 89 degrees, taking a value every 1 degree, and calculating to obtain a value range meeting the condition intersection point b in the step two.

Step four, when the condition is in the determined value range of b, setting y to tan theta (x + b) and y to tan omega x + a⁺Has an intersection of (x)₀,y₀) The intersection of y ═ tan θ (x + b) and y ═ tan ω · x + a is (x ═ tan ω · x + a)₀′,y₀′)；x₀Between (M +1) d and Md;

if x₀If the light ray is not between (M +1) d and Md, the incident light ray and the light-blocking ring have an intersection point, namely the light ray firstly irradiates the light-blocking ring, and the light ray automatically meets the condition of primary scattering elimination;

if x₀Between (M +1) d and Md, then there is no intersection point between the incident ray and the light-blocking ring, i.e. the ray first hits the cylinder wall, then the mathematical expression of the condition of primary scattering cancellation is:

(x₀,y₀) And (0, -a)⁺) Is connected to x_mIntersection (x) of Md (i.e. light-blocking rings with closely positioned incident light rays)_m,y_m) Within the light-blocking ring, i.e. y_m≥a-Md tanω；

Therefore, within the value range of b, discrete sampling is carried out at small intervals, (for example, a is 300mm, and b is 0.1mm), the satisfaction condition of the conditions in the step two is calculated, and the number of rays which cannot satisfy the conditions at the incident angle is recorded.

Step five, aiming at each group a⁺And d, superposing the number of the rays which do not meet the conditions under all the angles to obtain the total number of the rays which do not meet the conditions.

Step six, storing the total number of the unsatisfied light rays as AND (a)⁺D, the matrix element is zero, then the group a⁺And d can realize the primary scattering elimination design.

Finally, according to the a obtained in the step six⁺And d, calculating the value range of M, selecting the proper length of the light shield according to the actual engineering situation, finally obtaining the dimensions of the outer contour and the inner light blocking ring of the conical light shield shown in the figure 1, and completing the structural design of the stray light eliminating shield.