AddingSensorsToPR2 tutorial errors

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Hi guys,

I am going through the urdf/Tutorials/AddingSensorsToPR2 tutorial. This tutorial basically shows how to add new links and attach sensors to a link in gazebo. Although the new links and joints can be added and viewed properly:

I can find the ROS topic for the added camera. Here is a part of my xacro file, slightly modified from the original file on the tutorial page.

 <gazebo reference="finger_tip_camera_link">
  <sensor:camera name="finger_tip_camera_sensor">
    <imageSize>640 480</imageSize>
    <imageFormat>BAYER_BGGR8</imageFormat>
    <hfov>90</hfov>
    <nearClip>0.01</nearClip>
    <farClip>100</farClip>
    <updateRate>25.0</updateRate>
    <controller:gazebo_ros_camera name="finger_tip_camera_controller" plugin="libgazebo_ros_camera.so">
      <alwaysOn>true</alwaysOn>
      <updateRate>25.0</updateRate>
      <imageTopicName>finger_tip_cam/image</imageTopicName>
      <cameraInfoTopicName>finger_tip_cam/camera_info</cameraInfoTopicName>
      <frameName>finger_tip_camera_link</frameName>
      <interface:camera name="finger_tip_camera_iface" />
    </controller:gazebo_ros_camera>
  </sensor:camera>
  <turnGravityOff>true</turnGravityOff>
  <material>PR2/Blue</material>
  </gazebo>

I didn't see any error message, just couldn't find the ROS image topic, which should be finger_tip_cam/image in this case.

Any idea what goes wrong and where can I find the documentation on the syntax of gazebo_plugin. The Ros Camera Plugin XML Reference and Example here is fairly limited, not detailed enough for me to understand...