diff --git a/.asset/cat_dog.jpeg b/.asset/cat_dog.jpeg
new file mode 100644
index 0000000..8b30a3c
Binary files /dev/null and b/.asset/cat_dog.jpeg differ
diff --git a/README.md b/README.md
index 431dc56..7bf05af 100644
--- a/README.md
+++ b/README.md
@@ -151,13 +151,27 @@ nvidia-smi
 Replace `{GPU ID}`, `image_you_want_to_detect.jpg`, and `"dir you want to save the output"` with appropriate values in the following command
 ```bash
 CUDA_VISIBLE_DEVICES={GPU ID} python demo/inference_on_a_image.py \
--c /GroundingDINO/groundingdino/config/GroundingDINO_SwinT_OGC.py \
--p /GroundingDINO/weights/groundingdino_swint_ogc.pth \
+-c groundingdino/config/GroundingDINO_SwinT_OGC.py \
+-p weights/groundingdino_swint_ogc.pth \
 -i image_you_want_to_detect.jpg \
 -o "dir you want to save the output" \
 -t "chair"
  [--cpu-only] # open it for cpu mode
 ```
+
+If you would like to specify the phrases to detect, here is a demo:
+```bash
+CUDA_VISIBLE_DEVICES={GPU ID} python demo/inference_on_a_image.py \
+-c groundingdino/config/GroundingDINO_SwinT_OGC.py \
+-p /comp_robot/liushilong/data/pretrained/grounding_pretrain/groundingdino_swint_ogc.pth \
+-i .asset/cat_dog.jpeg \
+-o logs/1111 \
+-t "There is a cat and a dog in the image ." \
+--token_spans "[[[9, 10], [11, 14]], [[19, 20], [21, 24]]]"
+ [--cpu-only] # open it for cpu mode
+```
+The token_spans specify the start and end positions of a phrases. For example, the first phrase is `[[9, 10], [11, 14]]`. `"There is a cat and a dog in the image ."[9:10] = 'a'`, `"There is a cat and a dog in the image ."[11:14] = 'cat'`. Hence it refere to the phrase `a cat` .
+
 See the `demo/inference_on_a_image.py` for more details.
 
 **Running with Python:**
diff --git a/demo/inference_on_a_image.py b/demo/inference_on_a_image.py
index 207227b..0dd332f 100644
--- a/demo/inference_on_a_image.py
+++ b/demo/inference_on_a_image.py
@@ -11,6 +11,7 @@ from groundingdino.models import build_model
 from groundingdino.util import box_ops
 from groundingdino.util.slconfig import SLConfig
 from groundingdino.util.utils import clean_state_dict, get_phrases_from_posmap
+from groundingdino.util.vl_utils import create_positive_map_from_span
 
 
 def plot_boxes_to_image(image_pil, tgt):
@@ -80,7 +81,8 @@ def load_model(model_config_path, model_checkpoint_path, cpu_only=False):
     return model
 
 
-def get_grounding_output(model, image, caption, box_threshold, text_threshold, with_logits=True, cpu_only=False):
+def get_grounding_output(model, image, caption, box_threshold, text_threshold=None, with_logits=True, cpu_only=False, token_spans=None):
+    assert text_threshold is not None or token_spans is not None, "text_threshould and token_spans should not be None at the same time!"
     caption = caption.lower()
     caption = caption.strip()
     if not caption.endswith("."):
@@ -90,29 +92,56 @@ def get_grounding_output(model, image, caption, box_threshold, text_threshold, w
     image = image.to(device)
     with torch.no_grad():
         outputs = model(image[None], captions=[caption])
-    logits = outputs["pred_logits"].cpu().sigmoid()[0]  # (nq, 256)
-    boxes = outputs["pred_boxes"].cpu()[0]  # (nq, 4)
-    logits.shape[0]
+    logits = outputs["pred_logits"].sigmoid()[0]  # (nq, 256)
+    boxes = outputs["pred_boxes"][0]  # (nq, 4)
 
     # filter output
-    logits_filt = logits.clone()
-    boxes_filt = boxes.clone()
-    filt_mask = logits_filt.max(dim=1)[0] > box_threshold
-    logits_filt = logits_filt[filt_mask]  # num_filt, 256
-    boxes_filt = boxes_filt[filt_mask]  # num_filt, 4
-    logits_filt.shape[0]
+    if token_spans is None:
+        logits_filt = logits.cpu().clone()
+        boxes_filt = boxes.cpu().clone()
+        filt_mask = logits_filt.max(dim=1)[0] > box_threshold
+        logits_filt = logits_filt[filt_mask]  # num_filt, 256
+        boxes_filt = boxes_filt[filt_mask]  # num_filt, 4
+
+        # get phrase
+        tokenlizer = model.tokenizer
+        tokenized = tokenlizer(caption)
+        # build pred
+        pred_phrases = []
+        for logit, box in zip(logits_filt, boxes_filt):
+            pred_phrase = get_phrases_from_posmap(logit > text_threshold, tokenized, tokenlizer)
+            if with_logits:
+                pred_phrases.append(pred_phrase + f"({str(logit.max().item())[:4]})")
+            else:
+                pred_phrases.append(pred_phrase)
+    else:
+        # given-phrase mode
+        positive_maps = create_positive_map_from_span(
+            model.tokenizer(text_prompt),
+            token_span=token_spans
+        ).to(image.device) # n_phrase, 256
+
+        logits_for_phrases = positive_maps @ logits.T # n_phrase, nq
+        all_logits = []
+        all_phrases = []
+        all_boxes = []
+        for (token_span, logit_phr) in zip(token_spans, logits_for_phrases):
+            # get phrase
+            phrase = ' '.join([caption[_s:_e] for (_s, _e) in token_span])
+            # get mask
+            filt_mask = logit_phr > box_threshold
+            # filt box
+            all_boxes.append(boxes[filt_mask])
+            # filt logits
+            all_logits.append(logit_phr[filt_mask])
+            if with_logits:
+                logit_phr_num = logit_phr[filt_mask]
+                all_phrases.extend([phrase + f"({str(logit.item())[:4]})" for logit in logit_phr_num])
+            else:
+                all_phrases.extend([phrase for _ in range(len(filt_mask))])
+        boxes_filt = torch.cat(all_boxes, dim=0).cpu()
+        pred_phrases = all_phrases
 
-    # get phrase
-    tokenlizer = model.tokenizer
-    tokenized = tokenlizer(caption)
-    # build pred
-    pred_phrases = []
-    for logit, box in zip(logits_filt, boxes_filt):
-        pred_phrase = get_phrases_from_posmap(logit > text_threshold, tokenized, tokenlizer)
-        if with_logits:
-            pred_phrases.append(pred_phrase + f"({str(logit.max().item())[:4]})")
-        else:
-            pred_phrases.append(pred_phrase)
 
     return boxes_filt, pred_phrases
 
@@ -132,6 +161,12 @@ if __name__ == "__main__":
 
     parser.add_argument("--box_threshold", type=float, default=0.3, help="box threshold")
     parser.add_argument("--text_threshold", type=float, default=0.25, help="text threshold")
+    parser.add_argument("--token_spans", type=str, default=None, help=
+                        "The positions of start and end positions of phrases of interest. \
+                        For example, a caption is 'a cat and a dog', \
+                        if you would like to detect 'cat', the token_spans should be '[[[2, 5]], ]', since 'a cat and a dog'[2:5] is 'cat'. \
+                        if you would like to detect 'a cat', the token_spans should be '[[[0, 1], [2, 5]], ]', since 'a cat and a dog'[0:1] is 'a', and 'a cat and a dog'[2:5] is 'cat'. \
+                        ")
 
     parser.add_argument("--cpu-only", action="store_true", help="running on cpu only!, default=False")
     args = parser.parse_args()
@@ -144,6 +179,7 @@ if __name__ == "__main__":
     output_dir = args.output_dir
     box_threshold = args.box_threshold
     text_threshold = args.text_threshold
+    token_spans = args.token_spans
 
     # make dir
     os.makedirs(output_dir, exist_ok=True)
@@ -155,9 +191,15 @@ if __name__ == "__main__":
     # visualize raw image
     image_pil.save(os.path.join(output_dir, "raw_image.jpg"))
 
+    # set the text_threshold to None if token_spans is set.
+    if token_spans is not None:
+        text_threshold = None
+        print("Using token_spans. Set the text_threshold to None.")
+
+
     # run model
     boxes_filt, pred_phrases = get_grounding_output(
-        model, image, text_prompt, box_threshold, text_threshold, cpu_only=args.cpu_only
+        model, image, text_prompt, box_threshold, text_threshold, cpu_only=args.cpu_only, token_spans=eval(token_spans)
     )
 
     # visualize pred