.htaccess directory name uppercase to lowercase

Question

http://website.com/SUBfolder/filename.php

I need to convert "SUBfolder" to "subfolder".

I do not want to change the case of the actual filename only if its a directory I need it to be lowercase.

I do not want this to be handled in php. I need it to be handled directly in htaccess.

This is not the same question as other posts because I do not want to edit anything accept htaccess and I do not want to edit apache files