My camera pro working properly but view black screen

namespace NPR
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        Capture cap;
        Bitmap image;

        private void button1_Click(object sender, EventArgs e)
        {
            cap = new Capture();
            Application.Idle += new EventHandler(mycam);
        }

        void mycam(object sender, EventArgs e) 
        {
            image = cap.QueryFrame().ToBitmap();
            pictureBox1.Image = image;
        }   
    }
}