Specifications

THE LENSES

The DK2 model includes two pairs of lenses, termed the “A” and “B” lenses. The “A” lenses are

for those with 20/20 vision and are installed in the headset by default. The “B” lenses (shown

in Figure 1.9) are for those who are very nearsighted.

Figure 1.9: The “B” Lenses

The pairs are identical in terms of how they transmit light. How they differ is that they

place the lens at slightly different distances from the actual display. Combined with the

headset distance adjustment knobs, this allows the user to vary the distance between the

screen and the lenses, as well as the lenses and the eyes (commonly referred to as ‘eye

relief’), in order to accommodate a wide variety of facial characteristics as well as users who

require prescription glasses.

Note that the DK2 does not allow you to change the distance between the lenses. It is fixed

at 63.5 mm apart. However, this isn’t as much of an issue as one might suspect. The lenses

are designed to present the same image to the user regardless of where exactly the eyes are

located. If you move an image-capturing device (your eye, for instance) off the center axis of

the lens, the image captured does not itself move laterally. As long as they’re within a volume

about 1.5x1.5cm across and 0.5cm deep, barring a small amount of distortion at the edges,

your eyes will perceive the same image from the screen, with the same pixel appearing

‘directly ahead’. This allows the Rift to support a broad swath of users with varying inter-

pupillary distances. This remarkable property is called collimated light and will be discussed in

detail in Chapter 4.

THE POSITIONAL CAMERA

To track the user’s head position, the DK2 uses a camera (Figure 1.10) to detect infrared lights

located in the headset (hidden behind the front of the headset). You’ll notice that the lens of

the camera is mirrored as it only tracks infrared light.

other simple mistakes. These will be cleaned up during production of the book by copyeditors and proofreaders.

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