Let's first explore the optical rotary encoder.

让我们先来探索一下光学旋转编码器。

Scroll wheels commonly use either optical rotary  encoders or magnetic rotary position sensors in order to measure rotational motion.

滚轮通常使用光学旋转编码器或磁性旋转位置传感器来测量旋转运动。

One thing to note is that in this video we covered just two methods to measure rotational motion: an  optical encoder and a magnetic position encoder.

需要注意的一点是，在本视频中，我们只介绍了两种测量旋转运动的方法：光学编码器和磁性位置编码器。

However, it is possible to have an absolute optical encoder which has a disk that looks  like this, where different angles have different sections open to let the light through.

然而， 可以有一个绝对光学编码器， 它有一个看起来像这样的圆盘，其中不同的角度有不同的部分打开以让光线通过。

First, the incremental optical encoder from earlier can't read out an absolute angular  position because the wheel has 48 equally spaced spokes, and it can't discern one angle from the  next.

首先， 早期的增量式光学编码器无法读出绝对角度位置， 因为车轮有 48 个等距辐条，并且无法区分一个角度和下一个角度。