3D projector content has 3D data embedded on it to give views the simulation of seeing something in real-time. When you pair up 3D with crystal-clear resolution and fast frame rates similar to what you see in real life (real life doesn’t run in 24 Fps and can go beyond 60 Fps), the results are jaw-dropping.
With that said, let’s talk active and passive 3D. Do they use active shutter glasses or do they instead use passive lenses that filter out lights to produce a stereoscopic 3D result?
Are 3D Projectors Active or Passive?
3D projectors can be either active or passive. It depends on which 3D glasses a projector is using. Some use active shutter glasses that match the frame rate of frame-sequential 3D. Others use passive 3D glasses that have lenses that filter out light and isolate images from one eye to another.
3D projection involves putting identical images of different viewing angles on each eye in order to turn a 2D image into stereoscopic 3D. The images placed on your eye don’t even need to be slightly angled but instead be two identical images and you can get the same effect.
The best 3D videos though have alternate angles to make what you’re looking at appear truly three-dimensional. In any case, most projectors favor active 3D since most projectors use frame-sequential 3D.
You may also like: Your Complete Guide to 3D Projectors
What are Passive 3D Glasses?
Passive 3D glasses work by using polarized lenses to filter light from your projected image so that only a portion of the projected image is isolated on each eye. Passive 3D glasses are reminiscent of the classic red-and-blue 3D glasses that make black & white or monochrome films 3D.
Passive 3D glasses have the advantage of being relatively affordable when compared to active 3D glasses that require their own batteries to work. The main disadvantage of these products is that the image quality is poorer when compared to active 3D glasses.
Passive 3D glasses are more affordable than active 3D glasses alone but because they require a module to make your projector 3D support it, it’s more prohibitively expensive than you’d initially expect.
Further reading: How to Watch 3D Movies on a Projector
Filtration Effect of Polarized Lenses
This filtration effect on the image quality makes the 3D image look muddier and blurrier. These 3D glasses are also what cinemas used in order to do their own 3D movies in the late 2000s (such as Avatar from 2009). They’re cheaper to mass produce for a cinema’s audience.
Passive 3D glasses rely on a different optical principle compared to the frame sequential 3D system used by the majority of projectors. It won’t work as well with frame sequential like active 3D glasses would. You also need to buy an extra polarizing module for the sake of image conversion.
Make sure your media’s 3D supports passive 3D before making that passive 3D glasses purchase.
What are Active 3D Glasses?
Active 3D Glasses have more moving parts than their passive 3D counterparts. This is because they use shutters in order to isolate each image from one eye to another in a sequential fashion. They also work best with frame-sequential 3D.
The shutters can also come in the form of lenses that turn opaque or transparent depending on the frame that’s being projected by the 3D-Ready or Full 3D projector to save money on shutter-based mechanisms.
Lenses That Turn Opaque or Transparent
When a frame being projected is intended for the left eye based on frame-sequential 3D rules, your pair of active 3D glasses will only display the image on your left eye by turning the left lens transparent and the right lens opaque.
This is then done vice-versa with your right eye—the right lens becomes transparent and the left lens becomes opaque—on the next frame intended for your right eye. These frames come in rapid succession so that you can see one whole image instead of a shuttering effect.
Infrared Sensor Syncs with the Projector
The lenses use an infrared (IR) sensor embedded with the glasses in order to discern which eye should receive which frame in synchronization with the projector’s 3D data. The signal it receives could come from an external IR transmitter or the projector itself.
Even though passive 3D glasses and its module make the tech quite expensive, active 3D glasses and its IR-based technology will always remain more expensive with its lens shuttering or lens blocking tech that requires projector or transmitter synching to work.
What Do You Search for When Buying 3D Glasses?
Regardless if you buy glasses made by the projector manufacturer or not, there are still various factors to take into consideration that should assist in you selecting the right pair of glasses. To wit, consider the following.
- Weight
- Ergonomics
- Transmittance
- Viewing Angle
- Water Resistance
- Lower Power Consumption
- Panel (Lens) Response Time
- Contrast (Suggested Ratio of 1,000:1 to 1,500:1)
Most importantly, you should consider compatibility. Some 3D technology supports active 3D more than passive 3D or vice-versa.
Which Is Better? Passive 3D or Active 3D?
Both active and passive 3D glasses are expensive to purchase. You need to make sure you’re using the right glasses depending on the type of 3D being used by your projector (checkerboard, side-by-side, frame packing, or frame sequential).
Simply put, when it comes to frame-sequential 3D—the most common 3D tech available for projectors—active 3D glasses work better than passive ones. However, most media like streamed TV shows and movies use side-by-side 3D instead, which favors passive 3D glasses.
If you’re wondering which 3D glasses and technique is better, it mostly depends on the situation and circumstances. It comes on a case-by-case basis depending on the media you’re consuming, whether you’re using a 3DTV o 3D projector, or whether the tech best supports your brand of glasses.
Additional Tips
Passive 3D uses lenses to filter the images onto each eye while active 3D uses shutters in order to induce the same effect. Active 3D is more expensive and requires syncing between the mechanical 3D glasses and its shutters with the projector.
Passive 3D glasses work without needing batteries or synching. Passive is more affordable while 3D glasses and its shutter-based 3D work with frame-based, high-hertz 3D such as frame packed or frame-sequential 3D.
References:
- Jonah Matthes, “Do You Need a Special Screen for a 3D Projector?” TheHomeTheaterDIY.com, Retrieved July 12, 2021
- “3D Projectors and 3D Glasses: What to Know Before I Buy Them?“, BenQ.com, April 10, 2020