焦距计

例句：

1. 1. This camera has a built-in focus gauge to help you adjust the focus.
   这台相机内置了焦距计，可以帮助你调整焦距。
2. 2. The scientist used a focus gauge to measure the distance between the two objects.
   科学家使用焦距计测量两个物体之间的距离。
3. 3. The engineer used a focus gauge to ensure that the lens was properly focused.
   工程师使用焦距计确保镜头正确聚焦。