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As we all know by now, light gun games that worked on a CRT TV do not work on a plasma or LCD screen. However, in recent years an arcade game based on Rambo was released:

As you can see in that video, there appears a working light gun, on a modern LCD screen. There's also no tracking/pointer on the screen that you see with Wii shooters.

How does this light gun work on a non-CRT display?

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  • I have edited this question to remove the 100% off-topic secondary questions of why the developers used this technology, and why other companies haven't used it, to focus on the core of how the gun actually works, which is something we can (and have) answered. If you disagree that the changes have made this question on-topic, let's have a meta discussion about it. – Robotnik Jan 31 '20 at 1:27
  • Thanks for updating my 4 year old question and clearing up the confusion. – yesman Jan 31 '20 at 7:46
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The game uses infrared technology (IR emitters and sensors) to track the gun's position.

Following up on Yorik's answer, I went ahead and checked for the repair manual for this game. As mentioned, older light guns had to figure out what happened when the trigger is pulled by the way of technical trickery. In particular, most older games had to hard-code in the timing of light boxes (in relation to a CRT) to figure out if a hit was made, and which target was hit.

Moving on from there, There's many other ways to track and trigger on-hit detection. For this version of Rambo, I've found the following PDF installation and repair manual for it. What's interesting to note is that the DX version uses a SAMSUNG 56"DLP, (Which looks to be like a micro projector, but the manual uses the term CRT often.) but the two guns can be tested and tracked in real time. Likewise, there's a warning on having similar cabinets near each other due to interference, but there's a FREQ setting to help remedy issues. (This is the first sign of the answer as Infrared emitters are not "on" all the time, but can be set to a wavelength for a sensor to pick up on.)

First up, the gun itself uses the SEGA TYPE II GUN SENSOR (JPT-2030). There's not enough information I can find about this sensor, but we know that the gun's position is tracked on the screen in testing. Looking though the rest of the manual, I find that there's a IR Hood and Senor on the bottom of the screen. There does not seem to be any other technologies (like gyroscope or cameras) in use for tracking, so I'm going to have to assume that this game uses Infrared emitters for everything.

It's the same technology that's used for the Wii in just about every way. The only difference is that without a gyroscope, the gun can only detect if it sees the emitters or not. If there's no sign of the emitters, then it assumes it's off-screen to reload.

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    That clears things up! I was confused because I thought IR emitters, like the WIi, were very inaccurate (like my wiimote which needs constant recalibration). The gun in this game looks accurate no matter where you are, so I thought it would use a different technology. – yesman Oct 8 '15 at 4:53
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    The guns are tethered and the cabinet encourages a particular standing area. I suspect this is optimal for accuracy. I saw a manual for one of the house of the dead cabinets, and if I skimmed it correctly, they have a timing synch cable to connect cabinets, perhaps so that the IR emitters strobe out of synch (in addition to wavelength?) – Yorik Oct 8 '15 at 14:55
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Old CRT light guns worked by blanking the screen very briefly and then the gun detects bright light. Some worked by displaying bright regions sequentially. This happened quickly enough that the user wasn't aware.

CRTs fire a beam across the screen one line at a time starting from a corner, drawing horizontally (not unlike a typewriter filling a page). The old Nintendo method was to blank the screen when you pulled the trigger and then time how long it took for the gun to see the bright line being drawn.

Devices like the Wii, the xbone, etc now use two infrared light emitters separated by a fixed distance and the "light gun"/wiimote has an optical sensor that measures the point separation between these two sources. With the perceived separation, the known fixed distance, and some extra accelerometer data, the computer can triangulate the pointer position.

Note that a non-crt screen can still use the older blank screen method, just not the scanline timing method, but I expect that the Rambo game uses the infrared method.

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  • I think this spends too much effort explaining how old light guns work, where simply explaining new light guns would suffice – user106385 Oct 7 '15 at 22:14
  • Fair enough. The OP didn't (appear to) understand either type (witness the comment thread re: the wii) so, background is important. – Yorik Oct 8 '15 at 14:51

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