You can add this validator in your InputFilter function:
array(
'name' => 'Regex',
'options' => array(
'pattern' => '/^[0-9_\.\,]*$/',
'messages' => array(
\Zend\Validator\Regex::INVALID => 'Your error message.',
),
),
),
And you can add your character need to be accept for your input in the patterns(Regular Expression).
I hope this helps.