    QMainWindow(parent),
    ui(new Ui::CameraCalibration)
{
    ui->setupUi(this);
    this->setFixedSize(940,840);
    w1 = new First(this);
    w2 = new Second(this);
    QObject::connect(w2,SIGNAL(show_step1()),w1,SLOT(receive_step2()));
    QObject::connect(w1,SIGNAL(show_step2()),w2,SLOT(receive_step1()));