Used the libuvc_camera node instead of the usb_cam node because it allows to...

Used the libuvc_camera node instead of the usb_cam node because it allows to change the exposure time and has a nodelet version.
Changed the topics to coincide with the real robot.

launch/blob_detector.launch

+<!-- -->
+<launch>
+
+  <arg name="config_yaml_file" default="$(find iri_blob_detector)/config/default_params.yaml"/>
+
+  <group ns="usb_cam">
+    <node pkg="libuvc_camera" type="camera_node" name="mycam">
+      <!-- Parameters used to find the camera -->
+      <param name="vendor" value="0x046d"/>
+      <param name="product" value="0x0805"/>
+      <param name="serial" value="AB659260"/>
+      <!-- If the above parameters aren't unique, choose the first match: -->
+      <param name="index" value="0"/>
+
+      <!-- Image size and type -->
+      <param name="width" value="640"/>
+      <param name="height" value="480"/>
+      <!-- choose whichever uncompressed format the camera supports: -->
+      <param name="video_mode" value="uncompressed"/> <!-- or yuyv/nv12/mjpeg -->
+      <param name="frame_rate" value="15"/>
+
+      <param name="timestamp_method" value="start"/> <!-- start of frame -->
+      <param name="camera_info_url" value="file:///tmp/cam.yaml"/>
+      <param name="auto_exposure" value="0"/> <!-- use aperture_priority auto exposure -->
+      <param name="auto_exposure_priority" value="0"/>
+      <param name="exposure_absolute" value="0.90"/> <!-- use aperture_priority auto exposure -->
+    </node>
+  </group>
+
+  <node name="blob"
+        pkg="iri_blob_detector"
+        type="iri_blob_detector"
+        output="screen">
+    <param name="window_size" value="15"/>
+    <remap from="/blob/image_in/camera_info"
+             to="/usb_cam/camera_info"/>
+    <remap from="/blob/image_in/image_raw"
+             to="/usb_cam/image_raw"/>
+    <rosparam file="$(arg config_yaml_file)" command="load" />
+  </node>
+
+</launch>

launch/usb_cam_tag.launch

-<!-- -->
-<launch>
-
-  <node name="usb_cam"
-        pkg ="usb_cam"
-        type="usb_cam_node"
-        respawn="false"
-        output="screen">
-    <param name="video_device"    type="string" value="/dev/video0"/>
-    <param name="camera_frame_id" type="string" value="usb_cam"/>
-    <param name="pixel_format"    type="string" value="yuyv"/>
-<!--    <param name="io_method"       type="string" value="mmap"/>
-    <param name="image_width"     type="int"    value="1024"/>
-    <param name="image_height"    type="int"    value="768"/>
-    <param name="framerate"       type="int"    value="30"/>
-    <param name="pixel_format"    type="string" value="yuyv"/>
-    <param name="camera_info_url" type="string" value="file://$(find iri_blob_detector)/calibration/usb_cam.yaml" /> -->
-    <remap from="/usb_cam/camera_info"
-             to="/camera/camera_info"/>
-    <remap from="/usb_cam/image_raw"
-             to="/camera/image_raw"/>
-  </node>
-
-  <node name="blob"
-        pkg="iri_blob_detector"
-        type="iri_blob_detector"
-        output="screen">
-    <param name="window_size" value="15"/>
-    <remap from="/blob/image_in/camera_info"
-             to="/camera/camera_info"/>
-    <remap from="/blob/image_in/image_raw"
-             to="/camera/image_raw"/>
-    <rosparam file="$(find iri_blob_detector)/config/default_params.yaml" command="load" />
-  </node>
-
-</launch>