Light Pen Introduction
A light pen, an input device for an electronic computer, is used in conjunction with a display. It is sensitive to light, looks like a pen, and is connected to the host with a multi-purpose cable. You can perform operations such as drawing on the screen. A light sensor program that relies on a light pen program in the computer to input to the computer a light-sensitive sensor that displays characters or cursor position information on the screen. A light pen is an input device for computers. It has a simple structure, low price, fast response speed, and easy operation. It is often used in interactive computer graphics systems. In the graphics system, the light pen organically combines human intervention, display, and computer to form a man-machine communication system. The light pen can be used to select or modify the displayed graphics directly on the display screen.
The exterior of the light pen is a ball-point pen, which is composed of the pen body, lens group, optical fiber, switch, and wire. When working, the light pen accepts the light on the display screen and converts it into an electrical signal. After being amplified and shaped, it generates a pulse signal, which is input to the computer and sends an interrupt request to the computer. A graphic file stored in the display buffer memory represents a graphic entity.
This file is read out by the display controller in time sequence and translated into characters, vectors, etc., and then it is displayed on the screen by the character generator, vector generator, etc. through the electronic scanning beam. At this time, if the light pen stays at a certain position on the figure, the light pen sends an interrupt request because the light is detected, and the light pen program immediately freezes the display. The data state “frozen” on the display provides the computer with information such as the buffer memory address, the coordinate position of the main deflection counter, and the mode word of the controller. This information is the basis for the computer to process graphics according to human wishes.
How the light pen works:-
Light pens work in two ways: Pointing and Tracking.
① Pointing method
It divides the display screen into many small units in advance, and each unit has a corresponding number and meaning and is stored in the memory. These numbers and meanings correspond to the stored addresses respectively. Scanning on the display screen, when the light pen is pointed at a unit, a signal can be obtained as soon as the electron beam is swept over the unit, and the signal can be used to fetch the address of the unit from the memory to obtain the representation Meaning.
② Tracking method
It generates a cursor with a simple shape (such as a “ten” cursor) on the display screen in advance, and then points the cursor with a light pen and guides it to move freely. Where the lightpen moves, the cursor follows This is called lightpen tracking.
Light pen tracking is divided into two types:
Tracked is dragging the cursor on the display to change the position and show the “trajectory” of the action;
Trackless is just dragging Move the cursor on the display to change the position without leaving a “track”.
On a computer system, using these two functions of the lightpen, and then configuring the necessary programs, you can use the light pen to “talk” to the computer through the display, and you can use the light pen to draw various graphics on the display screen. A light pen is usually provided on the console of a large computer and on a graphic display.
Features of Light Pen:
1. Use a lightpen to complete a variety of complex tasks such as drawing, changing pictures, rotating graphics and zooming in and out, which is very useful in engineering design;
2. Select “Menu” to create a human-computer interaction interface;
3.Assisted editing programs to achieve editing functions. Lightpen input devices are important in computer-aided publishing systems. (With fiber optic connector Light).
Types of LightPen
1 Corded LightPen
2 Battery LightPen
3 Design LightPen
4 Let LightPen.
Light pens were manufactured by the following companies:
- REX data technology (REX 9541)
- Conrad Electronic
- Cardco, Inc (VC-20, C64)
- Future house (Educate Lightpen)
- Amicron Ltd. (Microscirbe Lightpen)
- Madison Computer (McPen Lightpen)
- Koala Soft
- Inkwell Systems (170-C and 184-C for cc65 )
- Turbo Computer
- Tech Sketch Inc
- Stack 100, Stack Computer Services Ltd.
- Trojan (C64 / 128, C16 / 116 / Plus / 4)
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