How to merge data from two different lasers

edit

I tried to use 1 hokuyo_node to publish to 'scan' and another hokuyo_node to publish to 'scan_1' I tried using the ira_laser_tool package but scan_mulit is not reaction.

<node pkg="ira_laser_tools" name="laserscan_multi_merger" type="laserscan_multi_merger" output="screen">
 <param name="destination_frame" value="/base_link"/>
 <param name="cloud_destination_topic" value="/merged_cloud"/>
 <param name="scan_destination_topic" value="/scan_multi_merged"/>
 <param name="laserscan_topics" value ="/scan /scan1" /> 
</node>

I use rosnode info /scan_multi show:

Node [/scan_multi]
Publications: None

Subscriptions: None

Services: None

cannot contact [/scan_multi]: unknown node

So,someone can tell me how to solve this problem. Thank you