The optical pickup unit has several components inside. First, lets take an overall look at this unit.

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Figure 22: Optical pickup unit.

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Figure 23: Optical pickup unit, back view. The arrows indicate the adjustment trimpots.

The optical pickup unit can be adjusted thru trimpots located on its back. These trimpots regulate the laser power. Sometimes you can fix an optical drive that isn’t reading discs or is having a lot of reading errors by adjusting these trimpots. We will write a tutorial on how to adjust the laser optical unit in the future.

Let’s take a look on the main lens. This lens is also known as objective lens and has two coils attached to it. This set is installed between two magnets. So, depending on the current direction applied to the coils the lens can move up or down, as the intensity of the current will tell how much it will move. So these coils controls the lens focus.

There are two other coils called tracking coils (below the plastic part on Figure 24) that control the lateral movement of the lens. Thru these coils the system can place the lens in the correct position.

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Figure 24: Main lens.