在事件中创建新线程

我在事件sensor_DepthFrameReady中创建了一个线程，但是当我执行它时，抛出了第 8 行（深度[深度]++;)在函数 SetImage1Frame 中并抛出此异常：

索引超出数组的范围。（深度 = -1）

出了什么问题？我认为该函数（SetImage1Frame）正在执行不止一次，但我仅在此方法中使用了此功能（sensor_DepthFrameReady）！！

    void sensor_DepthFrameReady(object sender, DepthImageFrameReadyEventArgs e)
    {
        short[] pixels;
        Thread th;
        using (frame=e.OpenDepthImageFrame())
        {
            if (frame!=null)
            {
                pixels = new short[frame.PixelDataLength];
                frame.CopyPixelDataTo(pixels);
                th = new Thread(() =>
                    SetImage1Frame(pixels));
                th.Start();
            }
        }     
    }
    int[] Depths=new int[4096];
    int depth=0;
    double chartBarWidth;
    void SetImage1Frame(short[] dpixels)
    {
        int maxValue = 0;
        for (int i = 0; i < dpixels.Length; i++)
        {
            depth = dpixels[i] >> DepthImageFrame.PlayerIndexBitmaskWidth;
            if (depth > 0)
            {
                Depths[depth]++;
            }
        }
        for (int i = 0; i < Depths.Length; i++)
        {
            maxValue=Math.Max(maxValue,Depths[i]);
        }
        for (int i = 0; i < Depths.Length; i++)
        {
            if (Depths[i] > 0)
            {
                stackPanel1.Dispatcher.Invoke(new Action(() =>
                {
                    Rectangle r = new Rectangle();
                    stackPanel1.Children.Add(r);
                }));
            }
        }
        image1.Dispatcher.BeginInvoke(new Action(() =>
        {
            WrbitmapImage.WritePixels(rect, dpixels, stride, 0);
        }));
    }

class Program
{
    static void Main(string[] args)
    {
        short s = unchecked((short)0x8001);
        int i = s >> 3;
        Console.WriteLine(i);
    }
}