diff --git a/cam_pose_aruco_board.py b/cam_pose_aruco_board.py
index b856d5f..cc69563 100644
--- a/cam_pose_aruco_board.py
+++ b/cam_pose_aruco_board.py
@@ -59,7 +59,7 @@ def process_video(detector: cv.aruco.ArucoDetector, board):
 		if k == ord('q'):
 			break
 
-def process(detector: cv.aruco.ArucoDetector, board: cv.aruco.GridBoard, img, mtx, dist, rvecs=None, tvecs=None, draw_marker_box=True, draw_marker_id=False, draw_marker_axis=True):	# Load previously saved data
+def process(detector: cv.aruco.ArucoDetector, board: cv.aruco.GridBoard, img, mtx, dist, r_vecs=None, t_vecs=None, draw_marker_box=True, draw_marker_id=False, draw_marker_axis=True):
 	gray = cv.cvtColor(img, cv.COLOR_BGR2GRAY)
 	(corners, ids, rejected) = detector.detectMarkers(gray)
 
@@ -73,17 +73,18 @@ def process(detector: cv.aruco.ArucoDetector, board: cv.aruco.GridBoard, img, mt
 
 	# Draw marker axis
 	if draw_marker_axis:
-		_rvecs, _tvecs, _ = cv.aruco.estimatePoseSingleMarkers(corners, markerLength=0.1, cameraMatrix=mtx, distCoeffs=dist)
-		for i in range(len(_rvecs)):
-			cv.drawFrameAxes(img, mtx, dist, _rvecs[i], _tvecs[i], 0.05)
+		_r_vecs, _t_vecs, _ = cv.aruco.estimatePoseSingleMarkers(corners, markerLength=0.1, cameraMatrix=mtx, distCoeffs=dist)
+		if _r_vecs is not None:
+			for i in range(len(_r_vecs)):
+				cv.drawFrameAxes(img, mtx, dist, _r_vecs[i], _t_vecs[i], 0.05)
 
 	if len(corners) > 0:
-		# Estimate pose of each marker and return the values rvec and tvec---(different from those of camera coefficients)
+		# Estimate pose of each marker and return the values r_vec and t_vec---(different from those of camera coefficients)
 		obj_points, img_points = board.matchImagePoints(corners, ids)
-		pose, rvec, tvec = cv.solvePnP(obj_points, img_points, mtx, dist, rvecs, tvecs)
+		pose, r_vec, t_vec = cv.solvePnP(obj_points, img_points, mtx, dist, r_vecs, t_vecs)
 		if pose:
 			# Draw Axis
-			cv.drawFrameAxes(img, mtx, dist, rvec, tvec, board.getMarkerLength()*1.5)
+			cv.drawFrameAxes(img, mtx, dist, r_vec, t_vec, board.getMarkerLength()*1.5)
 
 
 	cv.imshow('img', img)