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Passive Vs. Active 3D Technology

Bindu swetha
It's been ages since 3D technology was first put to use. In 1844, the stereoscope was invented which could take 3D photographic images. Today, the two new branches of this technology - passive and active 3D - have left users wondering which is better? Let's find out.

Did You Know?

People who have one dominant eye or are blind in one eye won't be able to see 3D images. This is because, the brain only receives one set of images and thus, interprets it as a 2D image.
3D technology is the three-dimensional version of image. Our brain does the post processing of the images that we see. It takes the input from our eyes and displays the images. 3D technology is nothing but tricking the brain so that it can perceive images as 3D. The inputs that are sent to the brain are slightly offset, and this is how 3D images are seen.
By making use of this technology, manufacturers have come up with devices that are 3D-enabled. The slight offset is created by having the shutter open and close at faster rates in active 3D, while in passive 3D, the polarization of vertical and horizontal lines does the trick.
However, of late, the glass-free devices have been developed which eliminates the use of the glasses and does the trick by creating a 3D screen. However, the image quality of such screens is still debatable. If you are curious to know which is better, this Entertainism write-up can help you.

Passive 3D Vs. Active 3D

Passive 3D


▪ Glasses: Polarized
▪ Cost of Glasses: Cheap
▪ Crosstalk: No
▪ Viewing Angle: Better
▪ Comfort: Light glasses

Active 3D


▪ Glasses: Liquid Crystal
▪ Cost of Glasses: Expensive
▪ Crosstalk: Present*
▪ Viewing Angle: Difficulty**
▪ Comfort: Heavy glasses

* - Due to high-speed shutter flickers
** - At few viewing angles, users may have difficulty in viewing (debatable)

Active 3D - How Does It Work?

The active 3D technology makes the use of glasses to create 3D images. In active 3D technology, the left eye shutter is open for a fraction of seconds while the right eye shutter is closed. This is followed by the right eye shutter being open while keeping the left eye shutter closed.
This is done at high speeds, and hence, we are unable to notice the blocking. As the brain post-processes the input from the eyes, these two images when fused create a 3D image. The glasses use liquid-crystal display (LCD) technology with IR (Infrared) sensors. These sensors are connected to the display, wirelessly.
The glasses are powered by using batteries and have a timing control. As per the timing signal's setting, due to the voltage applied by the batteries, the glass turns opaque once and then becomes transparent.
The IR sensors have a transmitter-receiver set that are synchronized to sense the refresh rate of the video signal (receiver set is in the glasses while transmitter set is in the television set), and then accordingly, sync the timing signal of the glass.
However, a drawback of this technology is the glasses that are used. They are battery-powered, bulky, and expensive. Many manufacturers do not provide a pair of glasses, so if you have more than one person watching the television set at a time, you will need to purchase these expensive glasses!

Passive 3D - How Does It Work?

Passive 3D technology also uses glasses like the active ones, but here the glasses are polarized. But, the initial 3D glasses were anaglyph. These glasses have two different color lenses which filter the images that are being displayed. Supposedly, the two colors are red and blue.
The blue color filter will only accept blue color from the image and leave out the others. The red color filter also does the same. So, the combined effect of these two colors will be a 3D image. However, these glasses didn't make use of the entire color spectrum and thus, the image quality was hampered.
Today, the more commonly used passive glasses are polarized. These glasses have filters that capture light only at a certain angle. This means that the right eye will capture light at a certain angle, say 45° while the left eye will capture light at 60°. The combined image will have the illusion depth due to angle offsets.
These glasses are preferred over the anaglyph glasses because there isn't any color distortion in the polarized glasses. The other way of putting the polarized technology is that each eye sees only a part of the frame from the image that is being displayed. One eye will be vertically polarized while the other will be horizontally polarized.
Thus, the combined illusion will be a 3D image. This means that out of 1080 horizontal lines that are available, only 580 lines are used. Thus, the image quality will be hampered. But, for the most common applications, this quality difference is hardly felt.
The passive glasses are not powered as there is no image sensing taking place here. Thus, the cost of the glasses is also lower than the active glasses.

Passive or Active 3D Technology - Which is Better?

Both the technologies have their pros and cons. The images in active 3D technology are crisp and have strong depth. However, the images viewed by the passive 3D technology are brighter but have black lines when viewed from shorter distances. But, when the quality of the image is taken into picture, active 3D is surely the winner.
Active 3D uses the horizontal lines in each frame that is displayed, i.e., 1080 lines are considered, but in passive technology, the number of lines are only 540 because one eye views the horizontal lines! And more the number of lines, better is the image quality. If you are looking for comfort, then you will surely be annoyed with the active glasses.
These are bulkier and expensive. Thus, you will always feel like you are wearing something heavy on your eyes. But, with passive glasses, this is not the case. The glasses are lighter and less expensive. So, even if you want to buy an extra pair of glasses, you will feel the pinch less if you have a passive glass.
So, it boils down to the quality versus price debate. If quality is what matters the most, active 3D-based applications are just the right choice. But, if you are running on a limited budget, it is advisable to go in for passive 3D. However, before making choice, it is better to try the glasses. You may not want to wear the bulkier active 3D glasses.
It is difficult to choose the "best" 3D technology from the active and passive technologies. The technology that suits the user preference and choice will be the apt 3D technology to choose. But before you buy the displays with these two technologies, make sure you have your preferences in place.