How to add stereo camera to UAV in gazebo

I’ve tried the Monocular camera, and it works successfully.
I edit the launch file like this:

    <!-- vehicle model and world -->
    <arg name="est" default="ekf2"/>
    <arg name="vehicle" default="iris"/>
    <!-- add stereo camera for iris -->
    <arg name="my_camera" default="iris_fpv_cam"/>
    <arg name="world" default="$(find mavlink_sitl_gazebo)/worlds/"/>
    <!-- also need to revise sdf -->
    <arg name="sdf" default="$(find mavlink_sitl_gazebo)/models/$(arg my_camera)/$(arg my_camera).sdf"/>
    <!-- <arg name="sdf" default="$(find mavlink_sitl_gazebo)/models/$(arg vehicle)/$(arg vehicle).sdf"/> -->

then I use rostopic list command, part of topics below:


it works, so I tried the same way on stereo

<arg name="my_camera" default="iris_stereo_camera"/>

then rostopic list
but nothing related to iris or image has shown up, nothing in rqt_image_view either.
I’m confused and don’t know why, I’d thank you for any advice!

use model in px4, not in .gazebo/models