Polarized 3D system

A 3D polarization system is a method for displaying stereoscopic 3D images. In this method, the images of the stereo image pair are broadcast in each opposes polarized light. There are correspondingly offset to each polarization filter in front of the projection lens and the 3D glasses, the viewer.

To maintain the polarization state of light a metal-coated screen is required. A normal white canvas would diffuse the light again and the channel separation would be repealed. The advantage of this projection technique is the high color fidelity of the images shown. Disadvantages are a filter for the light used by the waste and the metallic screen.

Meanwhile, this technique is applied not only to the projection, but also in LCDs, such as 3D displays and TVs. The basic principles are similar.

Technology

At the movies usually have a front projection is used, that is, the viewer and the projector are on the same side of the screen, then is projected onto a silver-coated or aluminum coated canvas that is able to reflect back the polarized light. In a rear projection screen is between the viewer and the projector and needs to pass the polarized light. The different images reach the screen by two different projectors and lenses. Another possibility is to use, only a projector when projecting ( called in RealD Z -screen projections ) by the left-right images alternately through a filter with alternating polarization. Even with 4K projectors can both fields are separated ( 2K ) in an image superimposed by a beam splitter again (Sony 4K 3D projection ). Use current 3D cinema projections in most cases, also the polarization technique. For details of the technology used in IMAX theaters see IMAX 3D.

The glasses needed also consists of two polarizing filters, each only the " fit " polarized light to pass through the corresponding view depending on polarization method, so that again each eye receives "his" image only. In the heyday of the first 3D film in the 1950s, most 3D movies were projected in black and white and color in this process.

One must distinguish between different polarization method procedures, and their orientations. There are two sets of polarization method: linear and circular. The two procedures are mutually incompatible. Within the method is also vital as the polarizing filters are aligned. For linearly polarized light the head while viewing the picture must be kept straight. If you hold the head to one side, the necessary for channel separation angle of 90 ° between the films changes from the projection lenses and filters in the glasses. This channel separation is no longer possible, it appear " ghosting ". This applies to both modern and Real -D method can no longer be, as they use circularly polarized light - you can move the head freely without disadvantages.

Another problem is the non-uniform use of the filters with different manufacturers of glasses, and projectors. The filters in the glasses must be suitable to the filters in the projector, otherwise there is a permutation of the channels.

Linearly

The linear polarization technique, the light is linearly polarized, i.e., the light oscillates in a plane defined by the filter. The filters for the left and right view must be aligned at right angles to each other to allow separation of the two views. At what angle, the polarization is aligned is irrelevant, provided that the polarization direction of the projection filter coincide with those of the glasses. The de facto standard for a linear projection is a "V " position of the filter, that is, the left swinging in -45 ° position ( \ ) and right in 45 ° (/). There are also other orientations, such as a position A, and the combination 0 ° / 90 ° or 90 ° / 0 °. Disadvantage of the linear polarization is that one perceives when tilting the head to the right or left crosstalk ( ghosting ) of the two views. This procedure applies to the company iZ3D monitors and in IMAX theaters use.

Circular

The circular polarization is somewhat difficult to understand. A circular polarization is at a phase difference between the two orthogonal linearly polarized shares before ( in which one can decompose each polarization ) of the same amplitude. The spatial and lateral amplitude curve you can imagine figuratively as a screw with left - or right-hand thread. It is usually produced by two successive filtering operations of unpolarised light. First, the non-polarized light is linearly polarized and then added with the aid of a Lambda/4-Verzögerungsfilters in rotation. The arrangement of the λ/4-Filters decides whether the rotation is counter-clockwise or clockwise. Here, the λ/4-Filter must be accurately aligned with the linear polarization of 45 °, to produce a clean circular oscillation. The circular filters are already available as a ready- welded filters generally, which are then referred to as left or right hand circular filter.

The separation of the two circular views is done with a matching circular polarized glasses. Here, the left-handed light are from dextrorotatory filter blocks (and vice versa). The orientation of the linear portion of the circular filter is also a factor. The linear portions of the projection screens must match the spectacle films. If this is not the case, you can see in high contrast color shift from black to dark blue to purple or white to yellowish. The orientation of the linear portion can be the same for left and right, because this proportion for the separation of the two views is irrelevant. Usual linear alignments are for RealD glasses 0 ° / 0 °, the original Polaroid circular glasses has 90 ° / 0 °.

Circular glasses for 3D monitors can have four different linear orientations. This is due to the pre-polarization of the LCD panels. Some 3D monitors have a RealD - orientation ( ie 0 ° / 0 ° ), eg Miracube 32 " and 46 " Hyundai 32 " and 46 " and JVC 46 ". Other monitors have a 45 ° / 45 ° orientation, eg Zalman 22 "and 24", Miracube 24 " Hyundai 22 " and 24 ". The Acer 3D laptop, in turn, has a different linear orientation: -45 ° / -45 ° ( = 135 °). The 3D-capable monitors have a line at a different polarization - that is, all straight lines are left-handed circularly polarized, polarized all odd lines dextrorotatory. For a S3D display the image information of the left and right view must be nested within each other ( interleaving ). The vertical resolution is halved due to the process. Advantage of circular polarization: You can also tilt your head when looking to perceive without crosstalk ( ghosting ). Currently circular polarization is used in most cinemas that use the polarization method, used to be used in disposable glasses in plastic RealD. The use of circular polarizing filters due to the double filter ( linear polarization λ / 4) is to be noted that these filters only work when they are positioned in the beam path in the correct direction, that is, the emergent light from the projector must first linear Polarizer penetrate. Conversely, in the eyeglasses of the first λ/4-Filter position into the beam path ( the linear portion thus indicates to the eye). If the filter is attached upside down, the filtering does not work anymore.