Fieldset class problem

Hello,
I am using cucumber(0.8.0), cucumber-rails (0.3.0) and capybara.
(0.3.8)
There is a scenario where i need to click a button but it does not
have a link ,id but it has a image under it.
The html code is as follows:
<fieldset class="submit_login">
  <input type="image" src="/images/bt.signup.png">
</fieldset>

How to proceed with this:

I had tried with the following code:
page.has_xpath?('/images/bt.signup.png') do
          click_link('/images/bt.signup.png')
end

After running it does not show me error but i am not sure whether it
is clicking or not.I am sure whether what i have done is correct or
not.
Also when we click on this then user is supposed to be created but
while searching for the user i am getting nil.
Please suggest.