This one should do the job.
$crits = array( '^F1' => xxxx,
'F2' => xxxx,
'^F3' => xxxx);
Or use
Utils_RecordBrowserCommon::merge_crits(array('F1' => xxx, 'F2' => xxx), array('F3' => xxx), true);
Crits are waiting to rewrite, because now full logic is not implemented. E.g. you can't do (F1 AND (F2 OR F3)) OR F4
Regards,
Adam