One way mirror vs tinted glass.

[Locke141]

When I went to get a quote for tinted glass I discovered I have no idea what I need/want. They asked if I wanted it bronzed and listed a bunch of different options. One options that stood out was to use one way mirror glass. It also turned out to be an affordable options as well, about 8,000 THS or about $4 USD a square foot. I was looking for the same kind of tinted glass that ever one else uses in there builds but think a one way mirror may work in my unusual build (see pic bellow).

I have no idea if the image quality would suffer, but am concerned there may be a blue tint. Does any one have ideas? I saw a one way mirror TV on HDTV once so thought this may be an options.

I think I'll probably go with tinted but may tray the one way first as it would have to run less then $16 and if it worked would be cool. What els do I need to know about tinted glass for arcade cabs?


http://forum.arcadecontrols.com/index.php/topic,146172.msg1520926.html#msg1520926

[Xiaou2]

When I went to get a quote for tinted glass I discovered I have no idea what I need/want. They asked if I wanted it bronzed and listed a bunch of different options. One options that stood out was to use one way mirror glass. It also turned out to be an affordable options as well, about 8,000 THS or about $4 USD a square foot. I was looking for the same kind of tinted glass that ever one else uses in there builds but think a one way mirror may work in my unusual build (see pic bellow).

I have no idea if the image quality would suffer, but am concerned there may be a blue tint. Does any one have ideas? I saw a one way mirror TV on HDTV once so thought this may be an options.

I think I'll probably go with tinted but may tray the one way first as it would have to run less then $16 and if it worked would be cool. What els do I need to know about tinted glass for arcade cabs?


http://forum.arcadecontrols.com/index.php/topic,146172.msg1520926.html#msg1520926

 Another term for these is "Half Silvered Mirrors".   They were used in Many Arcade machines.   One example is Asteroids Deluxe.  The monitor is mounted facing the sky - pointed at a 45 degree mounted, half silvered mirror.  Behind the mirror... there is a piece of artwork that is lit up in black-light.  The front monitor image appears to float in front of the background artwork as a result.

 There is no "Blue" or colored tint.    There is also no distortion of the image.   The image seen through the mirror may be a little darker.. much like smoked glass /  light sunglasses.

 The reflective surface should be on the front side, if you are using it like Asteroids Deluxe... bouncing the main image off the front surface. (else you may see a little ghosting of the images)   

 However, If you are just looking through it... using rear coating will be fine, and should be no visual distortion.

 In the case of certain type of games... they sometimes used different percentage levels of the silvered coating... to make them more or less translucent.

[Locke141]

Thanks Xiaou2,

That was very helpful.

[RandyT]

A "half silvered mirror" (which is also known as a "beamsplitter") is not ideal as a window for an arcade machine.  It's function is very different than that of tinted glass.  It is designed to reflect light which it does not pass, with as little absorption as possible.  Tinted glass (or acrylic) is designed to absorb light which it does not pass, usually with as little reflection as possible.  Expensive optical components called "neutral density filters" do pretty much the same thing as tinted glass, but are more precise.

If a beamsplitter is used as a window, and the surface of the monitor is at all reflective, the result will be annoying ghost images.  You don't want the light bouncing off the reflective surface of the beamsplitter, hitting the surface of the monitor and bouncing back.  A very good anti-reflective coating on the face of the monitor will minimize this, but it may still be seen as some blooming.  You may also see yourself overlayed on the game screen while you play, depending on the lighting in the room.  An optical coating can't be made to reflect in only one direction.  It would violate the laws of physics.  You would need a very expensive multi-layer filter arrangement to prevent the same amount of reflection from both sides.

No, unless you are overlaying an image over a reflected background, you will want to avoid this kind of material.  You will want something which absorbs the excess light, not reflect it.  i.e. Tinted material.

[Xiaou2]

 Thats not really true.

 As stated, many arcade machines use these mirrors... from the 50s  to the 90s and even the 2000s !!!

 With a Surveillance One way mirror... the effect works to reflect like a mirror... UNLESS... someone behind the mirror, in the room, turns on a light!   Once that happens... you can see right through the mirror.

 Which again, is why they use them on:

 Asteroids Deluxe
 Space Invaders Deluxe
 Discs of Tron
 Warlords
 Kasco's  Ninja Gun  (and pretty much every Electro-Mechanical Gun game)
 Video Pinball
 Gholly Ghost
 Some Shooting game by Namco?  that has a Soda-Can that explodes into pieces
 
 And many more...


 Effect Variants & Other fun Info:

 Terminator 2 - Rear of half silvered mirror is mostly painted black... with exception to Two silk-screened explosion stars.  There are flash bulbs placed behind these translucent star shapes...  and if you get hit in the game... they light up and create a hovering 3d explosion effect.   Many people never saw this effect... due to the fact that when the bulbs blew... the Operators never replaced them.

 Ninja Gun - Uses a similar setup like T2.  It has two rows of translucent white Ninja shapes, and a colored plastic plate in front of that painted shapes.  Lights light up in sequence, making it appear that Ninjas are flipping across the middle of the game... or are hanging from a cable up in the middle of the air... crossing hand over hand across the game field.

 Crater Raider - Uses a special curved first-surface mirror.   When you look at the game, is makes it appear that the monitor is wider and deeper.  Quite a cool effect.

 Kozmik Kroozr - Actually used a real physical UFO model.  The model actually spins around 360 degrees, and lights up with LEDs.   Much more than the Standard static backdrop! 

 There are also a few games that used such a mirror for Stereoscopic displays... using dual monitors.




 The Monitor Image should be more than bright enough to pass through the Reflective coating...  Especially considering that games like Asteroids Deluxe were backlit with low level Blacklight bulbs.

 Ghosting isnt caused by the reflection.  Its caused if the mirror coating is on the rear of the glass, rather than the front... and if you are bouncing the image off the front... vs passing the image directly through.


 And to be clear...  Generally speaking... the Artwork is NOT being reflected.   The monitor image on these games is in Front of the mirror, being reflected off the front surface of the mirror... while the lit up artwork, is Behind the mirror... and just passed straight through.

 Because the Monitor is in front,  it appears to hover over the top of the artwork...  in 3d.   Due to the 45 degree angle of the mirror... that means that the artwork is about 1.5 to 2 ft deep... causing good 3d depth effect.   In Discs of Tron Environmental... they took it even further.. and had pieces of artwork that were even closer to the mirror...  making 3 different distinct depths.

[Locke141]

Thanks guys,

For the equivalent of $12 I was thinking of trying it. If I can't get it to work to my satisfaction, just changing it out for tinted glass. But after reading what Randy posted, a problem has been made clear. In the cabs that did use one way glass, they had to use complicated setups to stop you from seeing your own reflection. The angle of I Incidence equaled the angle of reflections. Thats why the one way glass was set at about 45. You the player only see the monitor and the blacked out area around it. In my build the player would still probably see a bit of some unwanted reflection.

Thanks guys.

[Xiaou2]

No problem.

 The reason for the mirror at 45 degrees.. was so that the both the Monitor and what was Behind the monitor.. could be displayed at the same time.   Not anything to do with Reflections from the outside world.

 If that were the case... you would see reflections when looking at the Backdrop artwork that is Behind the glass as well.   And thats not the case.   Once the artwork is lit up inside... it nullifies the reflectivity... and the light passes right through the glass.   If you didnt turn on the monitor... you will only see the backdrop.   If you turned on the monitor... its brighter... and in front of the backdrop... so it overpowers the backdrop, and hovers in front of the backdrop.

 However... if you pop the Monitor BEHIND the glass... as if it were a backdrop... you get the same thing as a backdrop.   An image that passed right through the glass... as the reflectivity is overpowered from the light from the internal monitor.


 If I had a chance,  Id make a Dual LCD setup... that has an LCD on both sides of the half silvered mirror.  This would allow you to display a changing backdrop to match the game - in the rear end...  and the actual game being displayed in the front...   thus you would get the actual 3d stereoscopic depth thats Arcade Cabinet Accurate.

 Ive seen this kind of thing done with two widescreen tvs,  to make a stereocopic 3d display for movie watching.  (before 3d tvs were available in mass)

http://www.instructables.com/id/How-to-realize-a-Stereoscopic-3D-digital-photofram/step8/Final-considerations/

[Xiaou2]

Ok, heres a Video of a Dual Monitor setup for Stereo 3D




 As you can see,  no distortion or glare issues on the monitor located Behind the Half-Silvered mirror.

[RandyT]

As you can see,  no distortion or glare issues on the monitor located Behind the Half-Silvered mirror.

X2, you seem really to have no idea how these things work.  The reason a beamsplitter is at a 45 degree angle, is not only to direct an overlayed image toward the viewer, but that it also pushes unwanted reflections away from the viewer's field-of-view.  Angles are everything when it comes to using these, and providing examples of arcade machines where they were used correctly, has no bearing on their performance in the application indicated by the OP.

I worked in the optics industry for close to 14 years, which included every facet of not only making beamsplitters, but also using them extensively in glasses-free 3D displays.  My name is even on several patents related to the latter.  I do know what I am talking about.

[yotsuya]

I worked in the optics industry for close to 14 years, which included every facet of not only making beamsplitters, but also using them extensively in glasses-free 3D displays.  My name is even on several patents related to the latter.  I do know what I am talking about.

No, man, you don't understand. He used to manage an arcade back in the day! Back in the DAY!!! 

[Locke141]

So Randy,

What should I be asking for in tinted glass?

[DK1105]

I just recently ordered glass for one of my cabinets.  I ended up going with a greylight rather than greylight 14 just for cost reasons.  Greylight is just a lighter tinting but is mostly see through and just about same price a clear glass.  Greylight 14 is the really dark almost black you see on a lot of cabinets but is much more expensive because as it was explained to me the smoking process takes a long time and a few years ago had to be changed.  I think my glass for my space duel was roughly 25 bucks from Henderson Glass.

[RandyT]

What should I be asking for in tinted glass?

If going with glass, the greylight is what you want.  The number in the name is the percentage of light that is allowed to pass through.  Stay away from the bronze colored stuff, because it acts as a color filter and will shift the colors of your screen.  It can be corrected for with most monitors, but why bother if you don't need to.

The percentage of transmission is a preference, and it depends on the monitor and the effect you are looking for.  Those who don't want to bother with a monitor bezel, have a monitor capable of higher brightness (these are usually CRTs) and are using the machine in subdued lighting, will usually opt for the darker material.  Otherwise, the lighter material with a monitor bezel is a good choice.