RewriteEngine on
RewriteRule ^check(metric)?\.([A-Za-z0-9]+|.*)\.jpg$ /LFS_Checker/LFS_online_check.php?name=$2&template=&units=$1 [nc,ns]
RewriteRule ^check(metric)?([0-9]+)\.([A-Za-z0-9]+|.*)\.jpg$ /LFS_Checker/LFS_online_check.php?name=$3&template=$2&units=$1  [nc,ns]
RewriteRule ^random(metric)?\.([A-Za-z0-9]+|.*)\.jpg$ /LFS_Checker/LFS_online_check.php?name=$2&template=R&units=$1  [nc,ns]