diff --git a/XplorePlane/Events/MeasurementToolEvent.cs b/XplorePlane/Events/MeasurementToolEvent.cs
index 4356e45..cb561d3 100644
--- a/XplorePlane/Events/MeasurementToolEvent.cs
+++ b/XplorePlane/Events/MeasurementToolEvent.cs
@@ -51,4 +51,25 @@ namespace XplorePlane.Events
         public System.Drawing.Rectangle RoiRect { get; set; }
         public System.Collections.Generic.List<(System.Drawing.Point center, int radius, double sizeMm)> Detections { get; set; }
     }
+
+    /// <summary>
+    /// 黑底检测事件（进入ROI绘制模式）
+    /// </summary>
+    public class BlackBackgroundDetectionEvent : PubSubEvent { }
+
+    /// <summary>
+    /// 黑底检测ROI绘制完成事件
+    /// </summary>
+    public class BlackBackgroundRoiDrawnEvent : PubSubEvent<System.Windows.Int32Rect> { }
+
+    /// <summary>
+    /// 黑底检测结果事件
+    /// </summary>
+    public class BlackBackgroundResultEvent : PubSubEvent<BlackBackgroundResultPayload> { }
+
+    public class BlackBackgroundResultPayload
+    {
+        public System.Drawing.Rectangle RoiRect { get; set; }
+        public System.Collections.Generic.List<(System.Drawing.Point center, int radius, double sizeMm)> Detections { get; set; }
+    }
 }
diff --git a/XplorePlane/ViewModels/Main/MainViewModel.cs b/XplorePlane/ViewModels/Main/MainViewModel.cs
index 6f99e44..da2e756 100644
--- a/XplorePlane/ViewModels/Main/MainViewModel.cs
+++ b/XplorePlane/ViewModels/Main/MainViewModel.cs
@@ -278,6 +278,9 @@ namespace XplorePlane.ViewModels
             _eventAggregator.GetEvent<WhiteBackgroundRoiDrawnEvent>()
                 .Subscribe(OnWhiteBackgroundRoiDrawn, ThreadOption.UIThread);
 
+            _eventAggregator.GetEvent<BlackBackgroundRoiDrawnEvent>()
+                .Subscribe(OnBlackBackgroundRoiDrawn, ThreadOption.UIThread);
+
             NavigationTree = new ObservableCollection<object>();
 
             NavigateHomeCommand = new DelegateCommand(OnNavigateHome);
@@ -1055,8 +1058,96 @@ namespace XplorePlane.ViewModels
         private void ExecuteBlackBackgroundDetection()
         {
             if (!CheckImageLoaded()) return;
-            _logger.Info("Black background detection triggered.");
-            // TODO: 实现黑底检测逻辑
+            _logger.Info("Black background detection: entering ROI draw mode.");
+            _eventAggregator.GetEvent<BlackBackgroundDetectionEvent>().Publish();
+            StatusMessage = "黑底检测：请在图像上拖拽绘制矩形ROI";
+        }
+
+        private void OnBlackBackgroundRoiDrawn(System.Windows.Int32Rect roi)
+        {
+            try
+            {
+                var viewportVm = _containerProvider.Resolve<ViewportPanelViewModel>();
+                var imageSource = viewportVm?.ImageSource as System.Windows.Media.Imaging.BitmapSource;
+                if (imageSource == null) return;
+
+                System.Windows.Media.Imaging.BitmapSource gray8;
+                if (imageSource.Format != System.Windows.Media.PixelFormats.Gray8)
+                    gray8 = new System.Windows.Media.Imaging.FormatConvertedBitmap(
+                        imageSource, System.Windows.Media.PixelFormats.Gray8, null, 0);
+                else
+                    gray8 = imageSource;
+
+                int imgW = gray8.PixelWidth;
+                int imgH = gray8.PixelHeight;
+
+                int rx = Math.Clamp(roi.X, 0, imgW - 1);
+                int ry = Math.Clamp(roi.Y, 0, imgH - 1);
+                int rw = Math.Clamp(roi.Width, 1, imgW - rx);
+                int rh = Math.Clamp(roi.Height, 1, imgH - ry);
+
+                byte[] roiPixels = new byte[rw * rh];
+                gray8.CopyPixels(new System.Windows.Int32Rect(rx, ry, rw, rh), roiPixels, rw, 0);
+
+                using var roiImage = new Emgu.CV.Image<Emgu.CV.Structure.Gray, byte>(rw, rh);
+                for (int y = 0; y < rh; y++)
+                    for (int x = 0; x < rw; x++)
+                        roiImage.Data[y, x, 0] = roiPixels[y * rw + x];
+
+                // Otsu 二值化（黑底检测亮色区域：高于阈值为前景）
+                using var binary = new Emgu.CV.Image<Emgu.CV.Structure.Gray, byte>(rw, rh);
+                Emgu.CV.CvInvoke.Threshold(roiImage, binary, 0, 255,
+                    Emgu.CV.CvEnum.ThresholdType.Binary | Emgu.CV.CvEnum.ThresholdType.Otsu);
+
+                using var kernel = Emgu.CV.CvInvoke.GetStructuringElement(
+                    Emgu.CV.CvEnum.ElementShape.Ellipse, new System.Drawing.Size(3, 3), new System.Drawing.Point(-1, -1));
+                Emgu.CV.CvInvoke.MorphologyEx(binary, binary,
+                    Emgu.CV.CvEnum.MorphOp.Open, kernel, new System.Drawing.Point(-1, -1), 1,
+                    Emgu.CV.CvEnum.BorderType.Default, new Emgu.CV.Structure.MCvScalar(0));
+
+                using var contours = new Emgu.CV.Util.VectorOfVectorOfPoint();
+                using var hierarchy = new Emgu.CV.Mat();
+                Emgu.CV.CvInvoke.FindContours(binary, contours, hierarchy,
+                    Emgu.CV.CvEnum.RetrType.External, Emgu.CV.CvEnum.ChainApproxMethod.ChainApproxSimple);
+
+                const int minArea = 50;
+                double pixelSize = 0.139;
+
+                var detections = new System.Collections.Generic.List<(System.Drawing.Point center, int radius, double sizeMm)>();
+
+                for (int i = 0; i < contours.Size; i++)
+                {
+                    double area = Emgu.CV.CvInvoke.ContourArea(contours[i]);
+                    if (area < minArea) continue;
+
+                    var boundRect = Emgu.CV.CvInvoke.BoundingRectangle(contours[i]);
+                    double radiusF = Math.Max(boundRect.Width, boundRect.Height) / 2.0;
+                    var centerF = new System.Drawing.PointF(
+                        boundRect.X + boundRect.Width / 2.0f,
+                        boundRect.Y + boundRect.Height / 2.0f);
+
+                    var globalCenter = new System.Drawing.Point((int)centerF.X + rx, (int)centerF.Y + ry);
+                    double diameterMm = radiusF * 2 * pixelSize * 1000;
+
+                    detections.Add((globalCenter, (int)radiusF, diameterMm));
+                }
+
+                _eventAggregator.GetEvent<BlackBackgroundResultEvent>().Publish(
+                    new BlackBackgroundResultPayload
+                    {
+                        RoiRect = new System.Drawing.Rectangle(rx, ry, rw, rh),
+                        Detections = detections
+                    });
+
+                StatusMessage = $"黑底检测完成：检测到 {detections.Count} 个亮色区域";
+                _logger.Info("Black background detection: found {Count} bright regions in ROI ({X},{Y},{W},{H})",
+                    detections.Count, rx, ry, rw, rh);
+            }
+            catch (Exception ex)
+            {
+                _logger.Error(ex, "Black background detection failed");
+                StatusMessage = $"黑底检测失败: {ex.Message}";
+            }
         }
 
         private void ExecuteGrayscale()
diff --git a/XplorePlane/Views/Main/ViewportPanelView.xaml.cs b/XplorePlane/Views/Main/ViewportPanelView.xaml.cs
index 9be9e3d..a8a023d 100644
--- a/XplorePlane/Views/Main/ViewportPanelView.xaml.cs
+++ b/XplorePlane/Views/Main/ViewportPanelView.xaml.cs
@@ -142,21 +142,29 @@ namespace XplorePlane.Views
                 // 白底检测：进入ROI绘制模式
                 ea2?.GetEvent<WhiteBackgroundDetectionEvent>().Subscribe(() =>
                 {
-                    _whiteDetectDrawing = false;
-                    _whiteDetectMode = true;
-                    // 注册鼠标事件（只注册一次）
-                    RoiCanvas.PreviewMouseLeftButtonDown -= OnMainCanvasPreviewMouseDown;
-                    RoiCanvas.PreviewMouseLeftButtonDown += OnMainCanvasPreviewMouseDown;
-                    RoiCanvas.PreviewMouseMove -= OnMainCanvasPreviewMouseMove;
-                    RoiCanvas.PreviewMouseMove += OnMainCanvasPreviewMouseMove;
-                    RoiCanvas.PreviewMouseLeftButtonUp -= OnMainCanvasPreviewMouseUp;
-                    RoiCanvas.PreviewMouseLeftButtonUp += OnMainCanvasPreviewMouseUp;
+                    _bgDefectDrawing = false;
+                    _bgDefectRoiMode = BackgroundDefectRoiMode.WhiteBackground;
+                    RegisterBackgroundDefectRoiMouseHandlers();
+                }, Prism.Events.ThreadOption.UIThread);
+
+                // 黑底检测：进入ROI绘制模式
+                ea2?.GetEvent<BlackBackgroundDetectionEvent>().Subscribe(() =>
+                {
+                    _bgDefectDrawing = false;
+                    _bgDefectRoiMode = BackgroundDefectRoiMode.BlackBackground;
+                    RegisterBackgroundDefectRoiMouseHandlers();
                 }, Prism.Events.ThreadOption.UIThread);
 
                 // 白底检测：渲染结果
                 ea2?.GetEvent<WhiteBackgroundResultEvent>().Subscribe(payload =>
                 {
-                    RenderWhiteBackgroundResult(payload);
+                    RenderBackgroundDefectResult(payload.RoiRect, payload.Detections);
+                }, Prism.Events.ThreadOption.UIThread);
+
+                // 黑底检测：渲染结果
+                ea2?.GetEvent<BlackBackgroundResultEvent>().Subscribe(payload =>
+                {
+                    RenderBackgroundDefectResult(payload.RoiRect, payload.Detections);
                 }, Prism.Events.ThreadOption.UIThread);
             }
             catch { }
@@ -347,7 +355,25 @@ namespace XplorePlane.Views
             RoiCanvas.SelectedROI = null;
             if (DataContext is ViewportPanelViewModel vm)
                 vm.ResetMeasurementState();
-            SetStatus("已清除所有测量");
+
+            var canvas = FindChildByName<System.Windows.Controls.Canvas>(RoiCanvas, "mainCanvas");
+            if (canvas != null)
+            {
+                if (_bgDefectPreview != null)
+                {
+                    canvas.Children.Remove(_bgDefectPreview);
+                    _bgDefectPreview = null;
+                }
+                ClearBackgroundDefectOverlays(canvas);
+            }
+            else
+                _bgDefectOverlays.Clear();
+
+            _bgDefectDrawing = false;
+            _bgDefectRoiMode = BackgroundDefectRoiMode.None;
+            try { RoiCanvas.ReleaseMouseCapture(); } catch { /* 未捕获则无影响 */ }
+
+            SetStatus("已清除所有测量及白底/黑底检测结果");
         }
 
         private void SaveOriginalImage_Click(object sender, RoutedEventArgs e)
@@ -400,37 +426,54 @@ namespace XplorePlane.Views
 
         #endregion
 
-        #region 白底检测
+        #region 白底/黑底检测
 
-        private bool _whiteDetectMode;
-        private bool _whiteDetectDrawing;
-        private System.Windows.Point _whiteDetectStart;
-        private System.Windows.Shapes.Rectangle _whiteDetectPreview;
-        private readonly System.Collections.Generic.List<System.Windows.UIElement> _whiteDetectOverlays = new();
+        private enum BackgroundDefectRoiMode
+        {
+            None,
+            WhiteBackground,
+            BlackBackground
+        }
+
+        private BackgroundDefectRoiMode _bgDefectRoiMode;
+        private bool _bgDefectDrawing;
+        private System.Windows.Point _bgDefectStart;
+        private System.Windows.Shapes.Rectangle _bgDefectPreview;
+        private readonly System.Collections.Generic.List<System.Windows.UIElement> _bgDefectOverlays = new();
+        private bool _bgDefectMouseHandlersRegistered;
+
+        private void RegisterBackgroundDefectRoiMouseHandlers()
+        {
+            if (_bgDefectMouseHandlersRegistered) return;
+            RoiCanvas.PreviewMouseLeftButtonDown += OnMainCanvasPreviewMouseDown;
+            RoiCanvas.PreviewMouseMove += OnMainCanvasPreviewMouseMove;
+            RoiCanvas.PreviewMouseLeftButtonUp += OnMainCanvasPreviewMouseUp;
+            _bgDefectMouseHandlersRegistered = true;
+        }
 
         // 需要在 mainCanvas 的 MouseDown/Move/Up 中处理
         // 由于 PolygonRoiCanvas 内部已经处理了鼠标事件，我们通过 PreviewMouse 事件来拦截
 
         private void OnMainCanvasPreviewMouseDown(object sender, System.Windows.Input.MouseButtonEventArgs e)
         {
-            if (!_whiteDetectMode || e.LeftButton != System.Windows.Input.MouseButtonState.Pressed) return;
+            if (_bgDefectRoiMode == BackgroundDefectRoiMode.None || e.LeftButton != System.Windows.Input.MouseButtonState.Pressed) return;
 
             var canvas = FindChildByName<System.Windows.Controls.Canvas>(RoiCanvas, "mainCanvas");
             if (canvas == null) return;
 
-            _whiteDetectStart = e.GetPosition(canvas);
-            _whiteDetectDrawing = true;
+            _bgDefectStart = e.GetPosition(canvas);
+            _bgDefectDrawing = true;
 
             // 创建预览矩形（不清除之前的检测结果）
-            _whiteDetectPreview = new System.Windows.Shapes.Rectangle
+            _bgDefectPreview = new System.Windows.Shapes.Rectangle
             {
                 Stroke = System.Windows.Media.Brushes.Blue,
                 StrokeThickness = 1,
                 StrokeDashArray = new System.Windows.Media.DoubleCollection { 4, 2 }
             };
-            System.Windows.Controls.Canvas.SetLeft(_whiteDetectPreview, _whiteDetectStart.X);
-            System.Windows.Controls.Canvas.SetTop(_whiteDetectPreview, _whiteDetectStart.Y);
-            canvas.Children.Add(_whiteDetectPreview);
+            System.Windows.Controls.Canvas.SetLeft(_bgDefectPreview, _bgDefectStart.X);
+            System.Windows.Controls.Canvas.SetTop(_bgDefectPreview, _bgDefectStart.Y);
+            canvas.Children.Add(_bgDefectPreview);
 
             RoiCanvas.CaptureMouse();
             e.Handled = true;
@@ -438,45 +481,46 @@ namespace XplorePlane.Views
 
         private void OnMainCanvasPreviewMouseMove(object sender, System.Windows.Input.MouseEventArgs e)
         {
-            if (!_whiteDetectDrawing || _whiteDetectPreview == null) return;
+            if (!_bgDefectDrawing || _bgDefectPreview == null) return;
 
             var canvas = FindChildByName<System.Windows.Controls.Canvas>(RoiCanvas, "mainCanvas");
             if (canvas == null) return;
 
             var current = e.GetPosition(canvas);
-            double x = Math.Min(_whiteDetectStart.X, current.X);
-            double y = Math.Min(_whiteDetectStart.Y, current.Y);
-            double w = Math.Abs(current.X - _whiteDetectStart.X);
-            double h = Math.Abs(current.Y - _whiteDetectStart.Y);
+            double x = Math.Min(_bgDefectStart.X, current.X);
+            double y = Math.Min(_bgDefectStart.Y, current.Y);
+            double w = Math.Abs(current.X - _bgDefectStart.X);
+            double h = Math.Abs(current.Y - _bgDefectStart.Y);
 
-            System.Windows.Controls.Canvas.SetLeft(_whiteDetectPreview, x);
-            System.Windows.Controls.Canvas.SetTop(_whiteDetectPreview, y);
-            _whiteDetectPreview.Width = Math.Max(1, w);
-            _whiteDetectPreview.Height = Math.Max(1, h);
+            System.Windows.Controls.Canvas.SetLeft(_bgDefectPreview, x);
+            System.Windows.Controls.Canvas.SetTop(_bgDefectPreview, y);
+            _bgDefectPreview.Width = Math.Max(1, w);
+            _bgDefectPreview.Height = Math.Max(1, h);
         }
 
         private void OnMainCanvasPreviewMouseUp(object sender, System.Windows.Input.MouseButtonEventArgs e)
         {
-            if (!_whiteDetectDrawing) return;
+            if (!_bgDefectDrawing) return;
 
-            _whiteDetectDrawing = false;
-            _whiteDetectMode = false;
+            _bgDefectDrawing = false;
+            var completedMode = _bgDefectRoiMode;
+            _bgDefectRoiMode = BackgroundDefectRoiMode.None;
             RoiCanvas.ReleaseMouseCapture();
 
             var canvas = FindChildByName<System.Windows.Controls.Canvas>(RoiCanvas, "mainCanvas");
             if (canvas == null) return;
 
             var end = e.GetPosition(canvas);
-            int x = (int)Math.Min(_whiteDetectStart.X, end.X);
-            int y = (int)Math.Min(_whiteDetectStart.Y, end.Y);
-            int w = (int)Math.Abs(end.X - _whiteDetectStart.X);
-            int h = (int)Math.Abs(end.Y - _whiteDetectStart.Y);
+            int x = (int)Math.Min(_bgDefectStart.X, end.X);
+            int y = (int)Math.Min(_bgDefectStart.Y, end.Y);
+            int w = (int)Math.Abs(end.X - _bgDefectStart.X);
+            int h = (int)Math.Abs(end.Y - _bgDefectStart.Y);
 
             // 移除预览矩形
-            if (_whiteDetectPreview != null)
+            if (_bgDefectPreview != null)
             {
-                canvas.Children.Remove(_whiteDetectPreview);
-                _whiteDetectPreview = null;
+                canvas.Children.Remove(_bgDefectPreview);
+                _bgDefectPreview = null;
             }
 
             if (w < 10 || h < 10) return; // 太小忽略
@@ -485,34 +529,40 @@ namespace XplorePlane.Views
             try
             {
                 var ea = ContainerLocator.Current?.Resolve<Prism.Events.IEventAggregator>();
-                ea?.GetEvent<WhiteBackgroundRoiDrawnEvent>().Publish(new System.Windows.Int32Rect(x, y, w, h));
+                var rect = new System.Windows.Int32Rect(x, y, w, h);
+                if (completedMode == BackgroundDefectRoiMode.WhiteBackground)
+                    ea?.GetEvent<WhiteBackgroundRoiDrawnEvent>().Publish(rect);
+                else if (completedMode == BackgroundDefectRoiMode.BlackBackground)
+                    ea?.GetEvent<BlackBackgroundRoiDrawnEvent>().Publish(rect);
             }
             catch { }
 
             e.Handled = true;
         }
 
-        private void RenderWhiteBackgroundResult(WhiteBackgroundResultPayload payload)
+        private void RenderBackgroundDefectResult(
+            System.Drawing.Rectangle roiRect,
+            System.Collections.Generic.List<(System.Drawing.Point center, int radius, double sizeMm)> detections)
         {
             var canvas = FindChildByName<System.Windows.Controls.Canvas>(RoiCanvas, "mainCanvas");
-            if (canvas == null || payload?.Detections == null) return;
+            if (canvas == null || detections == null) return;
 
             // 绘制ROI矩形（蓝色实线）
-            var roiRect = new System.Windows.Shapes.Rectangle
+            var roiShape = new System.Windows.Shapes.Rectangle
             {
                 Stroke = System.Windows.Media.Brushes.Blue,
                 StrokeThickness = 1,
-                Width = payload.RoiRect.Width,
-                Height = payload.RoiRect.Height,
+                Width = roiRect.Width,
+                Height = roiRect.Height,
                 IsHitTestVisible = false
             };
-            System.Windows.Controls.Canvas.SetLeft(roiRect, payload.RoiRect.X);
-            System.Windows.Controls.Canvas.SetTop(roiRect, payload.RoiRect.Y);
-            canvas.Children.Add(roiRect);
-            _whiteDetectOverlays.Add(roiRect);
+            System.Windows.Controls.Canvas.SetLeft(roiShape, roiRect.X);
+            System.Windows.Controls.Canvas.SetTop(roiShape, roiRect.Y);
+            canvas.Children.Add(roiShape);
+            _bgDefectOverlays.Add(roiShape);
 
-            // 绘制每个检测到的黑色区域
-            foreach (var (center, radius, sizeMm) in payload.Detections)
+            // 绘制每个检测区域（白底为暗区、黑底为亮区，可视化相同）
+            foreach (var (center, radius, sizeMm) in detections)
             {
                 // 红色虚线圆
                 var circle = new System.Windows.Shapes.Ellipse
@@ -527,7 +577,7 @@ namespace XplorePlane.Views
                 System.Windows.Controls.Canvas.SetLeft(circle, center.X - radius);
                 System.Windows.Controls.Canvas.SetTop(circle, center.Y - radius);
                 canvas.Children.Add(circle);
-                _whiteDetectOverlays.Add(circle);
+                _bgDefectOverlays.Add(circle);
 
                 // 45°直径标注线（从圆心向左上到右下）
                 double offset = radius * 0.707; // cos(45°) * radius
@@ -542,7 +592,7 @@ namespace XplorePlane.Views
                     IsHitTestVisible = false
                 };
                 canvas.Children.Add(diamLine);
-                _whiteDetectOverlays.Add(diamLine);
+                _bgDefectOverlays.Add(diamLine);
 
                 // 尺寸标注（在斜线右上方）
                 string label = sizeMm >= 1000 ? $"{sizeMm / 1000:F2} mm" : $"{sizeMm:F0} μm";
@@ -556,15 +606,15 @@ namespace XplorePlane.Views
                 System.Windows.Controls.Canvas.SetLeft(text, center.X + offset + 3);
                 System.Windows.Controls.Canvas.SetTop(text, center.Y - offset - 14);
                 canvas.Children.Add(text);
-                _whiteDetectOverlays.Add(text);
+                _bgDefectOverlays.Add(text);
             }
         }
 
-        private void ClearWhiteDetectOverlays(System.Windows.Controls.Canvas canvas)
+        private void ClearBackgroundDefectOverlays(System.Windows.Controls.Canvas canvas)
         {
-            foreach (var el in _whiteDetectOverlays)
+            foreach (var el in _bgDefectOverlays)
                 canvas.Children.Remove(el);
-            _whiteDetectOverlays.Clear();
+            _bgDefectOverlays.Clear();
         }
 
         #endregion