Editing Optical disc drive (section)

=== Form factors ===
Optical drives for computers come in two main form factors: ''[[half-height]]'' (also known as ''desktop drive'') and ''slim type'' (used in [[laptop]] computers and [[Desktop computer#Compact|compact desktop computers]]). They exist as both internal and external variants.

''Half-height'' optical drives are around 4 centimetres tall, while ''slim type'' optical drives are around 1&nbsp;cm tall.

''Half-height'' optical drives operate upwards of twice the speeds as ''slim type'' optical drives, because speeds on slim type optical drives are constrained to the physical limitations of the [[#Rotational_mechanism|drive motor's rotation speed]] (around 5000[[rotations per minute|rpm]]<ref name="hughnews-BD">{{cite web |title=BluRay — Recording and reading speed |url=http://www.hughsnews.ca/faqs/authoritative-blu-ray-disc-bd-faq/8-recording-and-reading-speed |website=www.hughsnews.ca |access-date=11 August 2020 |quote=At this early stage anticipating anything is merely speculation but it's possible to make some informed predictions. From a practical perspective, spinning an optical disc at 10,000 RPM has long proven the realistic limit for half-height drives and 5,000 RPM for slim-types.}}</ref>) rather than the performance of the [[#Optical_pickup_system|optical pickup system]].

Because ''half-height'' demand much more electrical power and a [[voltage]] of 12 V DC, while ''slim'' optical drives run on 5 volts, external ''half height'' optical drives require separate external power input, while external ''slim type'' are usually able to operate entirely on power delivered through a computer's [[USB port]]. (In some slim drives, two USB connectors are required, each supplying power, but only one the data.) Half height drives are also faster than Slim drives due to this, since more power is required to spin the disc at higher speeds.

''Half-height'' optical drives hold discs in place from both sides while ''slim type'' optical drives fasten the disc from the bottom.

Half height drives fasten the disc using 2 spindles containing a magnet each, one under and one above the disc tray. The spindles may be lined with flocking or a texturized silicone material to exert friction on the disc, to keep it from slipping. The upper spindle is left slightly loose and is attracted to the lower spindle because of the magnets they have. When the tray is opened, a mechanism driven by the movement of the tray pulls the lower spindle away from the upper spindle and vice versa when the tray is closed. When the tray is closed, the lower spindle touches the inner circumference of the disc, and slightly raises the disc from the tray to the upper spindle, which is attracted to the magnet on the lower disc, clamping the disc in place. Only the lower spindle is motorized. Trays in half height drives often fully open and close using a motorized mechanism that can be pushed to close, controlled by the computer, or controlled using a button on the drive. Trays on half height and slim drives can also be locked by whatever program is using it, however it can still be ejected by inserting the end of a paper clip into an emergency eject hole on the front of the drive. Early CD players such as the Sony CDP-101 used a separate motorized mechanism to clamp the disc to the motorized spindle.

Slim drives use a special spindle with spring loaded specially shaped studs that radiate outwards, pressing against the inner edge of the disc. The user has to put uniform pressure onto the inner circumference of the disc to clamp it to the spindle and pull from the outer circumference while placing the thumb on the spindle to remove the disc, flexing it slightly in the process and returning to its normal shape after removal. The outer rim of the spindle may have a texturized silicone surface to exert friction keeping the disc from slipping. In slim drives most if not all components are on the disc tray, which pops out using a spring mechanism that can be controlled by the computer. These trays cannot close on their own; they have to be pushed until the tray reaches a stop. 
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