Visualization of the scene independent of the screen resolution

Hi All,
I’m developing a game with cocos2dx (cocos2d-2.1beta3-x-2.1.1) where the game scene has the size of a tiled map that I use as background. This game scene is bigger than the device screen and during the game I keep the player character in the center of the screen moving the layer’s camera. Here is the code:

    void GameLayer::zoomPoint(cocos2d::CCPoint position) {
      static cocos2d::CCSize screenSize = cocos2d::CCDirector::sharedDirector()->getWinSize();
      static float maxOriginDistanceX = ((m_sailingFieldMap->getContentSize().width - screenSize.width) * 0.5);
      static float maxOriginDistanceY = (m_sailingFieldMap->getContentSize().height - screenSize.height);

      // get the layer's CCCamera values
      float centerX, centerY, centerZ;
      float eyeX, eyeY, eyeZ;
      getCamera()->getCenterXYZ(&centerX, &centerY, &centerZ);
      getCamera()->getEyeXYZ(&eyeX, &eyeY, &eyeZ);

      centerX = eyeX = position.x;
      centerX = eyeX = cocos2d::clampf(centerX, - maxOriginDistanceX, maxOriginDistanceX);

      centerY = eyeY = (position.y - screenSize.height * 0.5f);
      centerY = eyeY = cocos2d::clampf(centerY, 0.0f, maxOriginDistanceY);

      getCamera()->setCenterXYZ(centerX, centerY, centerZ);
      getCamera()->setEyeXYZ(eyeX, eyeY, eyeZ);
    }

Now I have a problem, the visualization of the scene depends on the screen resolution. With iPad1 and iPad2 (1024x768) I have a good visualization, with iPad3 and iPad4 (2048x1536) the visualization is too small (in this case the tiled map is not enough width to fill the screen).
How can I resolve this problem avoding to prepare the same images with different resolutions?
Is there a way to solve the problem using the camera?
Consider that all my graphics stuff is a vectorial format then I can change the resolution of the png (I woluld like to avoid mantaing the same image in different png and resolution).

Thanks for the help.

Giannandrea