libuvc launch get permission denied opening usb error

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Hi all, new bee to ROS, I am following libucv, trying to run my webcam and publish to /camera/image_raw topic. Catkin_make is ok. but when I launch. I got permission denied opening errors like:

PARAMETERS
 * /camera/mycam/auto_exposure: 3
 * /camera/mycam/auto_white_balance: False
 * /camera/mycam/camera_info_url: file:///tmp/cam.yaml
 * /camera/mycam/frame_rate: 15
 * /camera/mycam/height: 480
 * /camera/mycam/index: 1
 * /camera/mycam/product: 0x0
 * /camera/mycam/serial: 
 * /camera/mycam/timestamp_method: start
 * /camera/mycam/vendor: 0x0
 * /camera/mycam/video_mode: uncompressed
 * /camera/mycam/width: 640
 * /rosdistro: indigo
 * /rosversion: 1.11.13

NODES
  /camera/
    mycam (libuvc_camera/camera_node)

ROS_MASTER_URI=http://localhost:11311

core service [/rosout] found
process[camera/mycam-1]: started with pid [12166]
**[ERROR] [1445862646.193876279]: Permission denied opening /dev/bus/usb/001/002**
[camera/mycam-1] process has died [pid 12166, exit code 255, cmd /home/visioner/libuvc_ws/devel/lib/libuvc_camera/camera_node __name:=mycam __log:=/home/visioner/.ros/log/f0455380-7b93-11e5-a62a-e4f89ca8e3f5/camera-mycam-1.log].
log file: /home/visioner/.ros/log/f0455380-7b93-11e5-a62a-e4f89ca8e3f5/camera-mycam-1*.log
all processes on machine have died, roslaunch will exit
shutting down processing monitor...

any ideas about this? I am pretty sure my cameras are OK, I could find in ls /dev/video* , I even write a simple opencv program showing that I can get my camera run.

Any ideas about this? Thanks!