问为什么不能使用queue显示返回的图片

EN

import cv2
cap = cv2.VideoCapture(0)
import queue
import threading

def capture(out_queue):
  while(True):
     frame = cap.read()[1]
     cv2.imshow('window', frame)
     if cv2.waitKey(1) & 0xFF == ord('q'):
        out_queue.put(frame)
        break

my_queue_1 = queue.Queue()
t1 = threading.Thread(target=capture, args=(my_queue_1,))
t1.start()
t1.join()
ret1 = my_queue_1.get()
print(type(ret1))
cv2.imshow('returned', ret1)
cv2.destroyAllWindows()
cap.release()