| 摘要 |
<p>The device has a housing (2). An optical system (2a) has two optical components, the distance relative to each other is adjustable for setting the focus of the optical system. An adjuster (5) is coupled to the two optical components, and regulates the distance between the two optical components. A detector detects the position of the optical components relative to one another. A processor (16) connects with the detector and converts the position data obtained from the detector into a focal length of the optical system. An output (17) is in connects to the processor for readable display of the converted focal length. A battery supplies energy to the detector, the processor and the output device.</p> |
