using server configuration instead of .htaccess in Phalcon, something can't be load

Question

My .htaccess files below:

##/.htaccess
<IfModule mod_rewrite.c>
    RewriteEngine on
    RewriteRule ^$ public/    [L]
    RewriteRule (.*) public/$1 [L]
</IfModule>

#/public/.htaccess
<IfModule mod_rewrite.c>
    RewriteEngine On
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteRule ^(.*)$ index.php?_url=/$1 [QSA,L]
</IfModule>

when I try using server configuration instead of .htaccess, something can't be load. my server configuration file below:

....
RewriteEngine On

RewriteCond %{DOCUMENT_ROOT}/public/%{REQUEST_FILENAME} !-d
RewriteCond %{DOCUMENT_ROOT}/public/%{REQUEST_FILENAME} !-f

RewriteRule ^/?public/(.*)$ /public/index.php?_url=/$1 [QSA,L]

RewriteRule  ^$ /public/    [L]
RewriteRule  (.*) /public/$1 [L]
....

when I get the image, it call error: ImgController handler class cannot be loaded

What's worng ? Thx.