What is the light gun principle of arcade and home machine?

First generation controller

Light gun controller of red and white machine (1984)

Early light gun game machines or toys were mostly composed of luminous guns and targets that could detect light, but video games were musical instruments.

The screen itself can't detect light, so the light gun of the TV game instrument adopts the opposite design. The light detector is installed inside the muzzle, and the aiming position is reversed by sensing the brightness of the TV screen.

The red and white machine light cannon adopts a relatively simple way. When shooting, the picture is blackened first, and then the target object is displayed on the picture in white blocks in turn. Determine which target the muzzle hit by the time when the light detector inside the muzzle detects the light. When there are more than 65,438+0 targets, the determination process is shortened by method of bisection method.

Because the above methods can't accurately determine which point the gun is aiming at, and the more target objects, the longer the determination process, so most of the TV game musical instrument light guns after SFC adopt more accurate scanning line detection methods.

Second generation controller

Second Generation Light Gun Controller (1993)

In the past, CRT screen, as the mainstream of TV screen, used cathode ray tube to emit electron beams to irradiate fluorescent substances on the screen surface, so that the fluorescent substances emitted three primary colors of red, green and blue light, and the electron beams swept across the whole screen in a Z-shaped trajectory from left to right, similar to the mode that word by word lines were broken to piece together a whole page of articles during typing.

The scanning line detection light gun grasps the aiming position of the muzzle by detecting the bright spot of electron beam scanning. When the player presses the trigger, the video game machine will make the screen flash with pure white and high brightness, and the photodetector will also start to work synchronously to detect the time when the electron beam scanning highlights pass through the muzzle lens. After that, the video game instrument can calculate the aiming position of the gun as long as it starts to output/ends to output/detects the bright spot of electron beam scanning from the picture.

Because the operation of light gun is very intuitive and simple, it fully satisfies the shooting fun that many players dream of, so it is widely welcomed by players all over the world, especially in the United States, where gun culture has a long history. Subsequent amusement devices include SFC, PS, SS, DC, PS2, Xbox, etc. The same type of controller is also introduced. GUNCON/GUNCON2 light gun is introduced into PS/PS2, and the accuracy is improved by inputting the image signal into the light gun for synchronous induction.

Because the scanning line detection light gun detects the aiming position by using the unique scanning imaging mode of CRT, it can't work on frequency doubling TV or non-scanning imaging LCD/plasma screen.

Principle of the second generation ray gun controller

Unlike what we thought, the light gun can only receive light, but can't emit light. After receiving the light, the light gun will send the signal of the gun aiming point back to the game machine, and the corresponding software will tell the host machine where the gun is aiming.

So how does the software measure the position? If you watch carefully, when pulling the trigger, whether the gun is aimed at the screen or not, there will always be a flash on the screen, and this white border controlled by software is the key to the positioning of the light gun. Before that, it is necessary for us to look at the imaging mode of interlaced scanning TV:

In the CRT TV of PAL\NTSC, scanning line is the way of image generation. Take NTSC as an example. Every time an image is scanned, instead of scanning 525 scanning lines continuously from beginning to end in one sixtieth of a second, only half of it is scanned, that is, 262.5 lines, and the remaining half is scanned in one sixtieth of a second. The first scan only scans odd lines horizontally from top to bottom, and the second scan scans even lines. The fields generated by the secondary scanning are combined into a complete image frame. Because the scanning is carried out alternately with odd and even scanning lines, it is called interlaced scanning.

After the trigger is pressed, the game software controls the host to send all-white frames. As mentioned above, TV display needs to scan this frame from top to bottom from left to right, so from the first point of scanning this frame, the muzzle receives white light (Note: Although the muzzle looks large, the acceptable range of the photosensitive mechanism that can really accept light is very small, so it will only aim at a small range on the screen, which is slightly larger than the distance between the two scanning lines. It can be considered as aiming at a "point"), the coordinate position can be calculated by the time difference T(pos), assuming that the propagation time of light from the screen to the light gun is 0. In the case of NTSC, the display time of interlaced frames is 0.0 167 seconds (60Hz). Here, in order to facilitate everyone to understand the calculation process, the ideal situation is tentatively set: scan line has no blanking time, frame has no blanking time, scan line retrace time is 0, and scan line is ***480 lines (there are actually 525 scan lines, but only about 480 lines have real imaging ability).

So the scanning time required for each scanning line is T(scanline)=0.0 167/480, so we can calculate.

Vertical position: Y=Trunc(T (position) /T (scan line))

Horizontal position: x = (t (pos)-y× t (scanning line)) /t (scanning line )× 640.

If all cases (scan line blanking, retrace, effective scan line, etc. ), the calculation process is much more complicated, but the principle is still based on the above de "ideal situation".

In fact, before sending all-white borders, the game machine will also send all-black borders, which can remove the interference of highlighted colors on the game screen.

Simply put, the working principle of light gun is:

Pull the trigger-the cable sends the signal to the host-the software commands the TV to send a white frame-the muzzle sends the received optical signal back to the host-the software calculates the time difference and the position-commands the TV to send the hit point-if it happens to be on the target, congratulations, you hit it!

Based on the above analysis, we can draw the following conclusion:

1, the light gun is harmless to the TV, because it only accepts light and does not emit light.

2. The light gun can't be used in progressive TV, because the imaging principle of progressive TV is completely different from that of interlaced TV. It scans continuously from the first scanning line to the last one of the screen images, instead of scanning odd lines first and then even lines. Of course, it cannot be applied to displays with TV cards and LCD devices. In fact, both SEGA and NAMCO have developed a ray gun system corresponding to advanced equipment, but it is unlikely to appear on home computers because of its high cost.

3. Other matters needing attention. A. The light gun cannot be used on the TV set below 14 inch; B for some old TV sets, it may be necessary to turn down the brightness and avoid fluorescent lamps to improve the positioning accuracy; C For some TV sets with excessive over-scanning ratio, it is normal that the edges may not be photographed, which is not the original light gun.

Third generation controller

Third Generation Light Gun Controller (2006)

Third generation light artillery

With the LCD screen gradually becoming the mainstream of TV screen, Nintendo took the lead in introducing the infrared sensing technology commonly used in the console of large-scale video game light gun to overcome this problem, and positioned the infrared camera at the front of the Wii remote controller through the infrared rays (invisible to the naked eye) emitted from the two ends of the infrared sensing bar installed on/under the screen.

As the standard handle of the Wii, the Wii remote controller itself has the function of a light gun, so the games of light gun type emerge one after another. Nintendo has also introduced a "Wii gun rack" around which the Wii remote controller can have a more realistic shooting experience after installation. Subsequently, NBGI also introduced a new generation of light gun "GUNCON3" in PS3, which also used two additional infrared positioning devices installed at the top of the screen to locate the infrared camera at the muzzle.