Articles: Monitors

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We have recently published a review of Zalman’s Trimon ZM-M220W, a monitor that can produce a stereoscopic or three-dimensional image. You may remember that the images for the left and right eyes were separated in that monitor by means of interlaced polarization. When you wore special eyeglasses (a passive device without any electronics), one eye saw only odd-numbered lines of the screen and the other eye saw even-numbered ones.

This method of creating a stereo image is not without drawbacks. It produces a three-dimensional, full-color and absolutely sharp picture indeed, and you can also use the monitor for both games and work, but the vertical resolution of the screen is reduced by half in 3D mode, and the interlacing of odd and even-numbered lines is noticeable in 2D mode. It seems as if the distance between the lines of pixels is increased in the matrix and you can clearly see the gaps.

However, Zalman is not the only maker of universal stereo monitors that support both 2D and 3D mode. I will tell you about the Trimon’s main opponent in this review. It is called iZ3D.

While the Trimon employs a matrix whose even- and odd-numbered lines produce light with different directions of polarization, the iZ3D goes further and employs two LCD matrixes of the same size (22 inches) and resolution (1680x1050 pixels). The operating principle of this monitor is based on the ability of liquid crystals to turn the polarization plane of the passing light by an angle that depends on the position of the crystals. This property is in fact used in every regular LCD monitor: the panel with liquid crystals is nestled in between two polarizers and the turning angle of the crystals determines what percent of light can pass through those polarizers.

So, the first matrix in the iZ3D is an ordinary LCD panel that produces the image proper. The polarization plane of its light is the same for every pixel of the panel. Intensity of light differs only.

The second matrix on top of the first one lacks polarizers and cannot regulate the intensity of light, but it can rotate the polarization plane of light emitted by specific pixels of the first panel by a certain angle. The human eye cannot normally perceive polarization, so the second matrix of the iZ3D looks just like a gray translucent panel.

But when you put on eyeglasses with polarizers set at 90 degrees to each other, the picture will be different. Now the amount of light for each eye depends not only on the brightness of the first panel but also on the polarization angle of light which goes out of the second panel.

One solution you may think about is to create something like Zalman’s Trimon: the second panel can be set up in such a way that its odd- and even-numbered lines made up different pictures and the eyes saw different lines when wearing polarizing eyeglasses. But like with the Zalman, this would reduce the effective vertical resolution twofold. We might use a tessellated pattern instead of odd- and even-numbered lines, of course… Anyway, in this design we somehow forget that the second matrix is an ordinary LCD panel and its state can be changed independently for each individual pixel at any given moment.

The iZ3D developers didn’t forget that. In their design each pixel of the first panel shows a combined picture for both left and right eyes whereas the second panel separates them. It is better explained with examples. For example, the right-eye lens of the eyeglasses has a polarization direction of 0 degrees and the left-eye lens, 90 degrees.

Suppose we need to show white to the left eye and black to the right eye. In this case the first panel of the monitor displays white and the second panel is set to a polarization of 0 degrees. As a result, the left lens lets the light pass while the right lens obstructs it.

What if the picture is then inverted so that the right eye saw white? The first panel doesn’t have to change anything. It is only necessary to turn the polarization plane by 90 degrees in the second panel, and the eyeglasses will show you a different picture.

And what if both eyes must see gray? It is simple: if the polarization plane is rotated by 45 degrees with the second matrix, each lens will let half the light pass and each eye will see gray. Note that this can be done for each out of the 1,764 million pixels individually.

To cut it short, the adjustment of the angle of polarization with the second matrix from 0 to 90 degrees changes the distribution of light from the first matrix between the right and left eyes. Thus, two things are needed to create a stereoscopic image on the iZ3D:

  • The pixels of the first matrix show the total of the images for the left and right eyes.
  • The pixels of the second matrix define what percent of light from each pixel of the first matrix comes to the left and right eye respectively.

The advantages of this design are obvious. To start with, this monitor can work as an ordinary 2D monitor. It has a full resolution of 1680x1050 for both 2D and 3D modes, and a full refresh rate of 60Hz in 3D mode. It works together with passive eyeglasses. One drawback can also be noted right away: the maximum brightness of the screen is not high, especially in 3D mode, because the light from the first matrix is distributed between the two eyes, so the effective brightness of the screen is reduced twofold. Some light is also additionally lost in the second matrix. This drawback is hardly serious, however. Ensuring a higher level of brightness for an LCD monitor is a technical problem that can be solved by employing more powerful backlight lamps.

Thus, the iZ3D represents an interesting solution and its method of creating a stereo image seems to be more promising than the one employed in the Zalman Trimon.

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