摘要：
RPC Photonics公司有高品質的的工程漫射體BSDF測試數(shù)據(jù)，但它對于FRED幫助甚少，下面這個步驟描述了如何利用FRED腳本轉換RPC Photonics提供的TXT文件，并將數(shù)據(jù)直接應用到FRED的Tabulated scatter 散射模型。
背景：
Thorlabs和RPC Photonics聯(lián)手共同推出的新型漫射體及光束整形技術，可以解決其他技術的不足，大大改善了諸如光刻系統(tǒng)、有效固態(tài)照明，顯示，背光，顯示亮度增強和投影屏等大多數(shù)應用的性能。這項我們稱之為工程漫射體（Engineered DiffusersTM）的新概念，與其他技術有許多不同。與諸如磨砂玻璃、乳色玻璃和全息元件等隨機漫射體截然不同，工程漫射體要求對于每個散射中心，通常為微透鏡單元，都進行控制。例如全息漫射體可以視為一組隨機排列的透鏡，但是通過全息曝光形成的類透鏡效果只能通過靜態(tài)方式進行控制：而無法單獨操控每個微透鏡單元，這也幫助解釋了全息漫射體無法控制光的分布和輪廓。另一方面，在工程漫射體中，每個微透鏡單元形成漫射體，由其凹形縱斷面和在陣列中的位置所確定。同時，為了確保漫射體不受輸入光束變化的影響，并且不產(chǎn)生衍射效果，微透鏡單元的分布是隨機的，根據(jù)產(chǎn)生相應的光束形狀函數(shù)所選取的概率分布函數(shù)來確定。因此，工程漫射體同時保留了隨機與確定性漫射體的優(yōu)點，從而實現(xiàn)高性能的光束整形功能。
FRED是美國Photon Engineering 公司開發(fā)的光學工程仿真軟件，其在雜散光分析中獨特的算法、高效的準確性，使其與其它同類產(chǎn)品相比更具優(yōu)勢。本案例我們重點講述如何由RPC Photonics的BSDF數(shù)據(jù)轉為FRED可識別的散射數(shù)據(jù)。
圖1. RPC Photonics工程漫射體結構及光束投射形狀
步驟
1、 在http://www.rpcphotonics.com/bsdf-data-optical-diffusers/下載并解壓BSDF數(shù)據(jù)到某一文件夾下，選擇“Raw data”文件。
圖2. RPC Photonics工程漫射體不同類型的散射數(shù)據(jù)
2、 將 http://fred-kb.photonengr.com/wp-content/uploads/sites/2/2015/06/constructRpcScatterFile.frs腳本文件放在步驟1中的文件下。（腳本代碼放在了本文的最后）
3、 打開FRED并運行腳本文件，會輸出如下“<SAMPLE>_FRED.txt”格式，<SAMPLE>即為RPC Photonics散射片數(shù)據(jù)集
例如下所示：
Sample name: EDF-C1-56
Merging data from file EDF-C1-56 0-0.txt
Finished merging RPC data for sample EDF-C1-56
FRED formatted data file: D:\FRED\散射片數(shù)據(jù)\EDF-C1-56_FRED.txt
4、 生成了FRED可識別的文件后，將散射模型導入到FRED里面
a. 創(chuàng)建一個新的散射庫
b. 散射模型命名
c. 改變散射模型為“Tabulated BSDF”.
d. 在File框出右鍵選擇“Replace With Data From a File”, 選擇步驟三生成的數(shù)據(jù)文件（如EDF-C1-56_FRED.txt ）
e. 切換為“Varies w/angle” 選項（假定所有的RPC Photonics datasets 數(shù)據(jù)有多個測試角度。
f. 在底部的對話框中，選擇透射散射、反射停并且你需要終止入射光線，
g. 點擊OK
5、 數(shù)據(jù)輸入后，可點擊“Plot”按鈕驗證BSDF模型及總的散射值
腳本代碼：
'#Language "WWB-COM"
Option Explicit
Sub Main
'Cleanup
ClearOutputWindow()
Print "Merging RPC Photonics BSDF Data Files"
SetTextColor(255,0,0)
Print "Note: Script should be located in the same folder as the BSDF TXT files."
Print "Note: Do not run this script multiple times without deleting the output file between executions."
SetTextColor(0,0,0)
'Current directory of this script (should be the same as the text files being merged)
Dim cDir As String
cDir = MacroDir$ & "\"
'Array which will be populated with the list of files to be merged
Dim fList() As String, curFile As String
GetFileList( cDir, fList )
Print ""
Print "Files found for merging:"
For Each curFile In fList
Print Chr(9) & curFile
Next
'Split the first text file name found to get the sample name. First file should be 0-0 measurement.
Dim nameArray() As String, sampName As String
nameArray = Split(fList(0)," 0-0.txt")
sampName = nameArray(0)
Print ""
Print "Sample name: " & Chr(9) & sampName
'Open an output file and write the FRED header data
Dim outFile As String
outFile = cDir & sampName & "_FRED.txt"
Open outFile For Output As #1
Print #1, "type bsdf_data"
Print #1, "format angles=deg bsdf=value scale=1"
'Loop the file list, skip the two header lines and write the remaining data to file
Dim lineArray() As String, curLine As Long
For Each curFile In fList
Print "Merging data from file " & curFile
ReadFile( cDir & curFile, lineArray )
For curLine = 2 To UBound(lineArray)
Print #1, lineArray(curLine)
Next
Next
'Close the output file
Close #1
Print "Finished merging RPC data for sample " & sampName
Print "FRED formatted data file: " & Chr(9) & outFile
End Sub
'Utility function to read the contents of a file into an array of strings.
Function ReadFile(ByVal fileName As String, _
ByRef lineArray() As String) As Long
ReadFile = -1
Dim oFSO As Object
Set oFSO = CreateObject("Scripting.FileSystemObject")
Erase lineArray
Dim fid As Long
If oFSO.fileexists( fileName ) Then
fid = FreeFile()
Open fileName For Input As fid
lineArray = Split(Input(LOF(fid), fid), vbCrLf)
Close fid
End If
Set oFSO = Nothing
Return UBound( lineArray )
End Function
Sub GetFileList( ByVal in_dir As String, _
ByRef in_flist() As String )
'Redimension the file list array
Erase in_flist
'Tracks how many files are found
Dim fCount As Long
fCount = 0
'Recurse directory and search for text files
Dim f As String
f = Dir$(in_dir & "*.txt")
While f <> ""
ReDim Preserve in_flist(fCount)
in_flist(fCount) = f
fCount += 1
f = Dir$()
Wend
ReDim Preserve in_flist(fCount-1)
End Sub
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