A computer privacy screen is an accessory that can be used to reduce the viewing angle of a monitor, laptop or even a cellular phone. Some privacy screens cause the display image to darken when viewed from an angle, while others make it appear very blurry. The image will typically be clear when viewed from straight on and become progressively harder to make out as the viewing angle is increased. Some privacy screens are designed to clip or slide on to a monitor, while others use adhesives or static electricity. In addition to offering increased security, a computer privacy screen can often protect against physical damage and provide some glare reduction.
Two main techniques are used to make computer privacy screens, both of which use similar layering technology that affects the transmission of light. A blurring computer privacy screen allows light to pass straight ahead, but obscures any that would normally leave at an angle. This light is still allowed to escape, which is why the screen can be viewed from an angle at all. Since the light is partially obscured, the image will appear blurry, leaving anyone who is standing to either side unable to read any text on the screen. Some of these privacy screens result in slight blurring when viewed straight on.
Darkening computer privacy screens work in a similar manner, but they completely block light that leaves the screen at an angle. This causes the screen to become progressively darker as the viewing angle increases, until there is no visible image at all. Similar to blurring filters, some darkening filters can result in a slight dimming of the image during normal usage. Both techniques are effective only with horizontal angles and cannot block the view of someone above or below the screen. This means that a computer privacy screen for a tablet device or cellular phone can be effective in landscape or portrait mode but not both.
There are also a number of different ways that a computer privacy screen can be attached. Units designed for use with cathode ray tube (CRT) monitors can typically clip onto the top of the screen bezel or slide over the outer diameter. Some screens that are designed for use with liquid crystal display (LCD) monitors also have this design. Other privacy filters can attach directly to a laptop screen, either with an adhesive or through static electricity. Cellular phone and tablet privacy screens typically attach the same way, though they are usually designed to cover the bezel of a device as well.