$captcha = new Zend_Form_Element_Captcha('captcha', array(
                    'captcha' => array(
                        'captcha' => 'Image',
                        'imgDir' => 'images/captcha',
                        'imgUrl' => 'images/captcha',
                        'width' => 150,
                        'height' => 50,
                        'fontsize' => 20,
                        'font' => '/usr/share/fonts/truetype/freefont/FreeMono.ttf',
                        'dotNoiseLevel' => 10,
                        'lineNoiseLevel' => 0,
                        'wordLen' => 5
                    )
                ));
        $captcha->setRequired(true)
                ->hasErrors();