为什么LogonUI.exe进程用户名为空，以及如何获取正确的用户名

Question

我正在尝试获取LogonUI.exe进程的用户名，但我变得空白。我怎样才能获得正确的用户名。

$logfile = 'C:\Users\Desktop\Process\log.txt'
if (!(Test-Path $logfile)) {
    New-Item $logfile -type file
}
do 
 {
 $owners = @{}
 gwmi win32_process |% {$owners[$_.handle] = $_.getowner().user}
 $data = get-process | select    processname,Id,PrivilegedProcessorTime,UserProcessorTime,@{l="Owner";e={$owners[$_.id.tostring()]}}
$allProcs = @(Get-WmiObject win32_process)

foreach($val in $allProcs) {    
$name = $val.ProcessName
"Before $name" | out-file -filepath $logfile -append
if ($name -eq 'LogonUI.exe') {
    $id = $val.Id
    $processtime = $val.PrivilegedProcessorTime.TotalMilliseconds
    $processtime1 = $val.UserProcessorTime.TotalMilliseconds
    $usename = $val.getowner().user
    "process value $name" | out-file -filepath $logfile -append
    "process value $id" | out-file -filepath $logfile -append
    #"process value $processtime" 
    #"process value $processtime1"
    "process value $usename" | out-file -filepath $logfile -append
    "Finished" | out-file -filepath $logfile -append
}
}
Start-Sleep -s 30
} while(1)

这里我试图获取LogonUI.exe进程的用户名我总是把它作为空白。如果我有多个用户登录到机器，则所有LogonUI用户名都显示为空白。如何获取LogonUI进程的正确用户名