Android : Android minimum exposure compensation

In android camera i am able to set the exposure compensation and lock the camera to minimum using the given methods

    params = mCamera.getParameters();
    params.setExposureCompensation(params.getMinExposureCompensation());
    params.setAutoExposureLock(true);

but still this is not the minimum exposure. In the program i do it by pointing the camera to a bright light source and then lock the camera exposure on click of a button. This is however not a good method. Is there any other way to reduce the exposure to absolute minimum?