THE LIGHT PEN
LIGHT PEN
A light pen is a computer input device in the form of a light-sensitive wand used in conjunction with a computer's display. It allows the user to point to displayed objects or draw on the screen in a similar way to a touchscreen but with greater positional accuracy. A light pen detects a change of brightness of nearby screen pixels when scanned by cathode ray tube electron beam and communicates the timing of this event to the computer. Since a CRT scans the entire screen one pixel at a time, the computer can keep track of the expected time of scanning various locations on screen by the beam and infer the pen's position from the latest timestamp.
Uses of Light Pens
Light pens are used in design work and by medical professionals to access and highlight medical records, and as hand-held bar code readers.
Advantages
Light pens are easy to use. They have extremely good positional accuracy on a computer screen, much more than is possible with a mouse or a touchscreen. They are ergonomically designed for ease of hand movement and are excellent for all drawing and pointing tasks. They don't require extra desk space and are easily modified for use by people with disabilities. When used for bar code reading, they are lightweight, able to come in direct contact with the bar codes and have no moving parts.
Disadvantages
Light pens are easily damaged. They can only be used on some computer screens; they do not work with LCD screens. They usually lack high resolution capability. They can be fatiguing to the hand if overused. They can impair viewing of the computer screen on which they're being used. When used as bar code readers, they have a high error rate.
A light pen is a computer input device in the form of a light-sensitive wand used in conjunction with a computer's display. It allows the user to point to displayed objects or draw on the screen in a similar way to a touchscreen but with greater positional accuracy. A light pen detects a change of brightness of nearby screen pixels when scanned by cathode ray tube electron beam and communicates the timing of this event to the computer. Since a CRT scans the entire screen one pixel at a time, the computer can keep track of the expected time of scanning various locations on screen by the beam and infer the pen's position from the latest timestamp.
Uses of Light Pens
Light pens are used in design work and by medical professionals to access and highlight medical records, and as hand-held bar code readers.
Advantages
Light pens are easy to use. They have extremely good positional accuracy on a computer screen, much more than is possible with a mouse or a touchscreen. They are ergonomically designed for ease of hand movement and are excellent for all drawing and pointing tasks. They don't require extra desk space and are easily modified for use by people with disabilities. When used for bar code reading, they are lightweight, able to come in direct contact with the bar codes and have no moving parts.
Disadvantages
Light pens are easily damaged. They can only be used on some computer screens; they do not work with LCD screens. They usually lack high resolution capability. They can be fatiguing to the hand if overused. They can impair viewing of the computer screen on which they're being used. When used as bar code readers, they have a high error rate.