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简介 .jJD$FC f#z:ILG= 人眼 光学模型可用来设计眼科用设备, 光学系统注定了要与人眼一起使用。本文演示了这样一个模型:Arizona眼睛模型,在Jim Schwiegerling教授的书中有详细描述:《Field Guide to Visual and Ophthalmic Optics》。AZ眼睛模型达到了基于平均临床数据所决定的轴上和轴外像差等级。FRED文件包含了此眼睛模型及几个用来分析它的 光源,并包括一个基于想要的屈光度来调整模型的内嵌脚本。 Lg<h54X ~cc }yDe 模型 ."wF86jW| (
v*xW. 模型的定义如表1种所示,由半径、圆锥常数、折射率、阿贝数、到下一面的距离等一系列表面组成。一些 参数由屈光度(A)来决定。 /ZyMD(_J Table 1. AZ眼睛模型的定义 rR6} 3CD#OCz7& 在FRED中使用0屈光度来创建的,光瞳加在了 透镜的前面。 材料是创建一个新的材料并选择类型“Model Material”,输入的参数是nd和vd. 5Npxs&Ea 7"!`<5o^ 光源 &|x7T<,) M
P8Sd1_= 多个光源定义来分析该模型的不同特性。图1显示了所以的光源和提示信息告诉您他们可以用来做什么。 @ujwN([I 1["i,8zB 图1. 光源和提示信息使用 j""ZFh04 '>
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K| 除了“Letter F”之外的所有光源的 光线位置设定在了孔径光阑位置处,并增加了pre-propagation distance= -8。尽管光线在光瞳处创建,规定的传输方向相对于光线位置在pre-propagation distance之后。这意味着 光束沿着Z轴在眼睛的前面以平行光入射,而不是在光瞳处入射。 pg%(6dqK4 x=cucZ 在往下看是内置的脚本用来修改屈光度,使其为4(250mm),光源“Letter F”在视网膜处生成一个字母为F的图像。绿色的光线聚焦的非常好而红色和蓝色光线有一点的模糊。使用Positions Spot Diagram分析工具来观察最为合适。 <|l}@\iRX 图2. 字母F光源的设定方法光 Qs\a&Q=0H ^=eC1bQA 图3. 字母F在视网膜上位置点列图 a <C?- g| eA7
Iv{M 视网膜的散射 +ydd"` 3RaW\cWzg 在散射文件中,有一个名为“Retina surface”的72%的反射型朗伯散射,它为视网膜的散射提供了一个粗略的近似。为了 模拟来自视网膜的散射,改变自定义元件“Eye ball” 下的视网膜的表面从“halt all” 到”Allow All”。并使几何中“plane”可追迹。 H$Kc~#= 1_t+lJI9j 图4. 视网膜朗伯散射设定 Srx:rUCv eN<L)a:J_ 注意在视网膜的表面有散射重点采样规格定义,在“Scatter”标签的底部可获取该信息。“toward pupil”指定散射光朝向光瞳,半角度10度。 X$5 2PAu>}W* 图5. 视网膜重点采样规格设定 ) (YNNu j{lurb)y 脚本 ,<IomA:q4 ?#w} S% 内置脚本使用对话框显示屈光度和光瞳直径的数值设置。使用FRED Basic脚本创建和使用对话框非常容易。图6显示了如何获取用户自定义对话框,如下图所示: {.2\}7.c 图6. 用户对话框的创建与编辑 Go{,<
gm 图7. 用户对话框编辑器 :EOai%i S L
5k^| 如果“OK”按钮按下,将会核对对话框下面的代码行,如果点击取消则脚本终止。然后输入的参数赋予变量,如果此处是保留为空白,则使用默认值。因此,如果没有值输入并点击“OK”按钮,则脚本是以屈光度为0,光瞳直径为4mm来运行的。 Zp)=l Td 余下的脚本计算与屈光度有关的所有参数。 s|WwBT R ABw(b 分析 ]L~NYe9 (T*$4KGV 屈光度为4,光瞳直径为4mm,字母F点在视网膜上所成的像。 &:l-;7d 图7. 字母F在视网膜上颜色分析 wj6u,+ KAnV%j 脚本代码 d1/WUKmbZ MS\vrq'_ - Option Explicit 'Remove this to enable non-dimensioned variables to be used.
-
- Dim entity As T_ENTITY
- Dim op As T_OPERATION
- Dim mat As T_MODELMATERIAL
- Dim A As Double
- Dim pupilDiam As Double
- Dim eID As Long
- Dim parID As Long
- Dim count As Integer
- Dim taq As Double, Rant As Double, CCant As Double, Rpost As Double, CCpost As Double
- Dim tlens As Double, nlens As Double
- Dim curv As Double, conic As Double
- Dim ok As Long
-
- Sub Main
-
- '用户输入对话框
- Begin Dialog UserDialog 320,126,"Input parameters" ' %GRID:10,7,1,1
- TextBox 220,21,40,21,.TextBox1 'default: 0
- Text 20,21,190,21,"Accommodation (in Diopters):",.Text1,1
- OKButton 40,91,90,21
- CancelButton 190,91,90,21
- Text 20,49,190,14,"Pupil diameter (4 mm default):",.Text2,1
- TextBox 220,49,40,21,.TextBox2 'default: 4
- End Dialog
- Dim dlg As UserDialog
-
- ok = Dialog (dlg)
-
- If ok=0 Then 'cancel button was pressed
- Print "Execution cancelled."
- End
- End If
-
- 'Assign accommodation and pupil diameter & use defaults if field left empty
- If dlg.TextBox1 = "" Then
- A = 0 'Default accommodation
- Else
- A = CDbl(dlg.TextBox1)
- End If
-
- If dlg.TextBox2 = "" Then
- pupilDiam = 4 'Default pupil diameter
- Else
- pupilDiam = CDbl(dlg.TextBox2)
- End If
-
- Print " "
- Print "Accommodation = " & A & " Diopters"
- Print "Pupil Diameter = " & pupilDiam & " mm"
-
- ' Calculate new parameters with accommodation
- taq = 0.55 + 2.97 - 0.04*A 'Aqueous thickness
-
- Rant = 12.0 - 0.4*A 'Radius of anterior lens
- CCant = -7.518749 + 1.285720*A 'Conic constant of anterior lens
-
- Rpost = -5.224557 + 0.2*A 'Radius of posterior lens
- CCpost = -1.353971 - 0.431762*A 'Conic constant of posterior lens
-
- tlens = 3.767 + 0.04*A 'Lens thickness
-
- nlens = 1.42 + 0.00256*A - 0.00022*A^2 'Lens index of refraction
-
- 'Adjust parameters to account for accommodation
-
- '*************************************************************************
- 'Aqueous thickness (Position of Lens)
- '*************************************************************************
- eID = FindFullName( "Geometry.Arizona Eye.Lens" )
- GetCustomElement eID, entity
-
- parID = FindFullName( "Geometry.Arizona Eye" )
-
- ' Delete any shift(s) in z
- count = 0
- While GetOperationCount(eID)>count
- GetOperation eID, count, op
- If op.Type="ShiftZ" Then
- DeleteOperation eID,count
- count=count-1
- End If
- count=count+1
- Wend
-
- 'Set new shift in
- op.Type = "ShiftZ"
- op.val1 = taq
- op.parent = parID
- AddOperation eID, op
- Print "Set aqueous humor thickness = " & taq-0.55
-
- '*************************************************************************
- 'Radius and conic constant of anterior lens
- '*************************************************************************
- eID = FindFullName( "Geometry.Arizona Eye.Lens.Anterior" )
- GetConic eID, entity, curv, conic
-
- SetConic eID, entity, 1/Rant, CCant
- Print "Set anterior lens radius = " & Rant & " and conic constant = " & CCant
-
- '*************************************************************************
- 'Radius and conic constant of posterior lens
- '*************************************************************************
- eID = FindFullName( "Geometry.Arizona Eye.Lens.Posterior" )
- GetConic eID, entity, curv, conic
-
- SetConic eID, entity, 1/Rpost, CCpost
- Print "Set posterior lens radius = " & Rpost & " and conic constant = " & CCpost
-
- '*************************************************************************
- 'Lens thickness (Position of posterior lens surface)
- '*************************************************************************
-
- parID = FindFullName( "Geometry.Arizona Eye.Lens" )
-
- ' Delete any z-shift(s)
- count = 0
- While GetOperationCount(eID)>count
- GetOperation eID, count, op
- If op.Type="ShiftZ" Then
- DeleteOperation eID,count
- count=count-1
- End If
- count=count+1
- Wend
-
- 'Set new z-shift
- op.Type = "ShiftZ"
- op.val1 = tlens
- op.parent = parID
- AddOperation eID, op
- Print "Set lens thickness = " & tlens
-
- '*************************************************************************
- 'Lens index of refraction
- '*************************************************************************
- eID = FindMaterial( "Lens" )
- GetModelMaterial eID, mat
-
- mat.Nd = nlens
- SetModelMaterial eID, mat
- Print "Set lens index of refraction = " & nlens
-
- '*************************************************************************
- 'Pupil diameter
- '*************************************************************************
- eID = FindFullName( "Geometry.Arizona Eye.Pupil.Iris" )
-
- 'Adjust pupil diameter (trimming volume inner hole)
-
- SetTrimVolHole eID, pupilDiam/2, pupilDiam/2, 0, 0, "Cylinder"
-
- ' Adjust pupil location to just in front of the lens
- parID = FindFullName( "Geometry.Arizona Eye" )
- eID = FindFullName( "Geometry.Arizona Eye.Pupil" )
- count = 0
- While GetOperationCount(eID)>count
- GetOperation eID, count, op
- If op.Type="ShiftZ" Then
- DeleteOperation eID,count
- count=count-1
- End If
- count=count+1
- Wend
- op.Type = "ShiftZ"
- op.val1 = taq-0.01
- op.parent = parID
- AddOperation eID, op
-
- Print "Set pupil diameter = " & pupilDiam
-
- 'Update AZ Eye subassembly Description
- eID = FindFullName( "Geometry.Arizona Eye" )
- GetEntity eID, entity
- entity.Description = "Accommodation = " & A & "D"
- SetEntity eID, entity
-
- Update
- Print "DONE!"
-
- End Sub
-
- 如果屈光度是4,光瞳直径是4,则会输出如下数据:
-
- Accommodation = 4 Diopters
- Pupil Diameter = 4 mm
- Set aqueous humor thickness = 2.81
- Set anterior lens radius = 10.4 and conic constant = -2.375869
- Set posterior lens radius = -4.424557 and conic constant = -3.081019
- Set lens thickness = 3.927
- Set lens index of refraction = 1.42672
- Set pupil diameter = 4
- DONE!
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