JP2012027427A - Stereoscopic display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a direct-view stereoscopic display requiring polarizing spectacles, which is free from vertical resolution degradation in stereoscopic viewing in comparison with non-stereoscopic viewing.SOLUTION: Two kinds of an R first picture composed by taking odd lines out of scanning lines of a left picture and a right picture being a stereoscopic pair, as a right picture and taking even lines as a left picture and an L first picture composed by taking odd lines as a left picture and taking even lines as a right picture are created and are alternately displayed on a liquid crystal display having an Xpol mounted thereon and driven at a double speed. A polarization axis variable liquid crystal plate which is transparent and changes only a polarization direction by 90° is placed over the liquid crystal having the Xpol mounted thereon, and the polarization direction is changed synchronously with rewriting positions of the L first picture and the R first picture. A backlight is provided with an extinction region and is extinguished in the picture rewriting positions. Polarizing spectacles are used, and a 1/4-wave plate is mounted in the front of the polarization axis variable liquid crystal plate if circularly polarizing spectacles are used. Thus, stereoscopic viewing with high resolution and simultaneous display of left and right pictures is realized.

Description

  The present invention relates to a direct-viewing stereoscopic display that is used as a television receiver and a computer display and separates left and right images using special glasses.

  Conventionally, there are a space division display method and a time division display method as means for displaying a binocular differential image on a thin direct view display. Each pair of dedicated glasses is used to separate the left and right images, enabling stereoscopic viewing.

  The space division display method is a method in which two left and right images are combined on a single screen and separated with special glasses. The mainstream at present is the so-called X-pole (hereinafter referred to as Xpol) system. This assigns right and left images to odd lines and even lines, respectively, changes the direction of polarization for each line by a polarizing plate and a special phase plate, and separates them with polarized glasses. There are two types of polarization, one using linearly polarized light and the other using circularly polarized light.

  Xpol includes a linear polarization type in which the polarization direction is different for each line and a circular polarization type in which the direction of rotation of the electric field vector is reversed. These are distinguished by being expressed as Xpol (1/2 wavelength plate) and Xpol (1/4 wavelength plate), respectively.

  The time-division display method is a method in which left and right images are alternately displayed on the screen and the refresh rate (refresh rate = number of times of rewriting per second) is increased to separate the left and right images with shutter glasses. There are two types of displays: liquid crystal and plasma. In general, a liquid crystal shutter is used as shutter glasses, and synchronization signals using infrared rays are transmitted and received in order to synchronize with the screen.

  The drawback of the Xpol method, which represents the space division method, is that the vertical resolution drops to half during stereoscopic viewing.

  The time division method is 120 Hz driving or 240 Hz driving to solve the flicker (flicker) of the screen itself, but it has a fundamental drawback in the case of moving image display. That is, when playing back or right and left images created by CG (computer graphics) at the same time, the left and right images are displayed alternately with time shifted, so when the subject moves, a stereo pair (stereo pair = a pair of left and right images for stereoscopic purposes) ) May not be recognized as an image, and there is a problem that stereoscopic vision is lost.

  It also requires shutter glasses. These glasses must be optically opened and closed alternately left and right, and synchronized with the alternately displayed images. For this reason, a liquid crystal shutter, a driving circuit, a synchronization signal receiving circuit, and a power source are required, which is heavy and expensive. Moreover, in order to improve the separation of the left and right images, a method such as reducing the opening time is taken, but there are disadvantages such as a dark screen.

  The biggest drawback is interference with fluorescent lamps. Computers and games under fluorescent lights cannot be concentrated due to flicker. In some liquid crystal stereoscopic displays, a linearly polarizing system is used, and a polarizing plate is removed from the surface polarizing plate, and a shutter is formed by a polarizing plate on the screen, a liquid crystal plate and a polarizing plate on the screen.

  In a plasma-type stereoscopic display, if a polarizing plate is attached to the screen, it becomes dark when viewing a 2D (two-dimensional) image without glasses, so the same hand cannot be used. The current situation is that the fluorescent light is kept from entering the eye as much as possible.

  The present invention simultaneously solves the above-described vertical resolution degradation of the space division display method, the moving image display problem of the time division display method and the problem of shutter glasses, and realizes a better direct-viewing stereoscopic display. For the purpose.

  A half-wave plate in which the direction of the slow axis is changed for each line is provided on the front surface of the liquid crystal display. This optical element is called Xpol (1/2 wavelength plate). As a result, the polarization direction for each line can be changed by 90 °. Xpol is transparent and can be used as a liquid crystal display for both 2D / 3D (2D / 3D) images.

  When displaying a stereo image, the right image of the stereo pair is assigned to the odd lines, the left image is assigned to the even lines, and the combined image, and the left image is assigned to the odd lines and the right image is assigned to the even lines. These two types are prepared and displayed at high speed and alternately. The former is called an R first image (meaning that the first line of the scanning screen is the right image) and is denoted as Rf. The latter is referred to as an L first image (meaning that the first line of the scanning screen is the left image) and is denoted as Lf.

  A liquid crystal plate (this is called a polarization axis variable liquid crystal plate) having a function of changing the polarization direction composed of a large number of horizontally long screen patterns by 90 ° is placed on the front surface of the above-mentioned 2D / 3D liquid crystal display. The polarization direction is sequentially changed by 90 ° from the top to the bottom of the screen in accordance with the rewriting positions of the R-first and L-first images. Thus, left and right original images divided into an R first image and an L first image can be obtained through polarized glasses.

  In this stereoscopic display, a white LED (light emitting diode) that can blink at high speed is used as a backlight, a horizontally long extinguishing area composed of a plurality of lines is provided, and the Rf image / Lf image rewriting position and the polarization axis variable liquid crystal are provided. Including the polarization axis switching position of the plate, and in synchronization with these, the position of the extinguishing region is sequentially moved from the top to the bottom of the screen, thereby avoiding poor separation of the left and right images due to the slow response speed of the liquid crystal. At the same time, the motion blur is improved.

  The method using linearly polarized glasses is superior to the method using circularly polarized glasses because a ghost (ghost = leakage of the other image separated and removed) occurs when the face is tilted. In this case, a ¼ wavelength plate is placed in front of the polarization axis variable liquid crystal plate, and the angle between the polarization axis and the slow axis is set to 45 °. As a result, it can be converted into circularly polarized light that rotates to the left and right. The left and right images can be separated and viewed stereoscopically through circularly polarized glasses that are reversely rotated from each other.

  Xpol, the polarization axis variable liquid crystal plate, and the quarter wavelength plate are all colorless and transparent, and can sufficiently withstand use as a 2D / 3D shared display.

  The glasses used are linearly polarized or circularly polarized filters. It is neither complicated nor expensive like shutter glasses. Light and less burden on humans.

  In the time division method, the left and right images of the stereo pair are alternately displayed at different times, so that the unnaturalness may be noticeable when the subject moves. This method follows the Xpol method, and the left and right images of the stereo pair are always displayed at the same time, and stereoscopic vision is not lost.

  Since L-first and R-first images are displayed in a time-sharing manner on a double-speed display, there is no flicker and no scan line is lost. Therefore, high-resolution stereoscopic viewing is possible.

Conceptual diagram showing improvement in vertical resolution during stereoscopic viewing The figure which shows the polarization direction for every line of L first image and R first image Diagram of the relationship between the polarization axis variable liquid crystal plate and the backlight linked with LCD rewriting The figure which shows the polarization transmission axis of LCD and the slow axis of Xpol (1/2 wavelength plate) Xpol (1/2 wavelength plate) incident polarization axis, slow axis, outgoing polarization axis relationship diagram Time relationship diagram of LCD and polarization axis variable liquid crystal plate rewriting and backlight blinking Configuration diagram of the present invention

  FIG. 1 is a conceptual diagram showing that the disadvantage that the vertical resolution is halved during stereoscopic viewing in the conventional method is improved by the new method. In other words, when the left and right original images 1L and 1R are interlaced, the L first image 2LR and the R first image 2RL are created and displayed alternately at high speed so that the vertical resolution is not reduced by the afterimage of the eye during stereoscopic viewing. It is.

  That is, in the conventional method, the image 3R from which the odd lines are separated from the R first image 2RL and the image 3L from which the even lines are separated are used as the right and left images, respectively.

  In the new method, the L-first image 2LR, which was not used in the conventional method, is used by time division multiplexing to solve the deterioration of the vertical resolution, and the left image 4L and the right image 4R are obtained.

  FIG. 2 is a schematic diagram of the Xpol method that enables separation of the synthesized left and right images. The polarization method will be described in the case of using circularly polarized light that does not generate ghost when the face is tilted. Conventionally, only the right R-first image 2RL (the right image on the odd lines and the left image on the even lines) is displayed on the display, and the left and right images are separated by using circularly polarized glasses whose left and right are opposite to each other. It was possible to see. Since the information of the left image L and the right image R can only be obtained every other line during stereoscopic viewing, the vertical resolution is naturally half that of the original image.

  The figure shown on the left side of FIG. 2 is an L first image 2LR (a left image on odd lines and a right image on even lines). In the L first image 2LR, it is necessary to reverse the direction of the circularly polarized light for each line with respect to the R first image 2RL. By displaying L-first and R-first images alternately, a stereoscopic image without deterioration in vertical resolution can be obtained through circularly polarized glasses.

  The liquid crystal display image is held until it is rewritten with the next image. Assuming that a 120 Hz drive display is assumed, rewriting takes place from the top to the bottom of the screen over 1/120 sec. If it demonstrates according to FIG. 3, the change of the polarization direction for every line of Xpol7 provided on LCD (liquid crystal display = liquid crystal display) 6 needs to be performed in synchronization with rewriting of a liquid crystal image.

  For this purpose, an element called a polarization axis variable liquid crystal plate 8 is prepared which sequentially changes the polarization direction by 90 ° from the top to the bottom of the screen, and is synchronized with the rewrite timing of the liquid crystal display. That is, the direction of linearly polarized light is rotated by 90 ° at the boundary 9 between the Rf (R first) image and the Lf (L first) image. That is, the boundary 10 of the polarization direction of the polarization axis variable liquid crystal plate and the boundary 9 of the image are completely matched, and the two liquid crystal plates are rewritten in 1/120 sec.

  In FIG. 3, an LED is used as the backlight, and the lighting and extinguishing areas are moved in synchronization with rewriting of the liquid crystal display. This is a means to reduce blurring when displaying moving images by reducing the afterimage of the eye, but by turning off the vicinity of the boundary between the image and the polarization direction, the separation of the left and right images due to the delay in the response speed of the liquid crystal is eliminated. This can be avoided and the number of division patterns of the polarization axis variable liquid crystal plate can be reduced. The reason for using LEDs instead of fluorescent tubes is that the response speed is a problem. The ratio between the turn-off time and the turn-on time is determined experimentally in consideration of brightness and blurring of moving images.

  It is not preferable to use a TN (twisted nematic) type liquid crystal as the polarization axis variable liquid crystal plate. The reason is that two modes of normally white (normally white = display white when no electric field is applied) and normally black (normally black = display black when no electric field is applied) are switched and used. In the normally black mode, there is a strong coloring phenomenon, and there is no workaround because two modes are used.

  A pi-cell liquid crystal plate is known as a liquid crystal element that changes the polarization direction at a high speed. This employs a horizontal electric field method, and the liquid crystal molecules rotate in the same plane. As a result, there are features such as a high-speed response, a wide viewing angle, and a high contrast ratio, and there are no coloring problems of the TN liquid crystal. Therefore, using a pi-cell liquid crystal plate as a component of the present invention is one option.

  In order to change the polarization direction using the polarization axis variable liquid crystal plate 8, the light emitted from Xpol 7 needs to be linearly polarized light. Therefore, Xpol 7 used in FIG. 3 is a half-wave plate. FIG. 4 shows the slow axis 12 of the half-wave plate for each line of Xpol.

FIG. 5 shows a state where the polarization transmission axis 11 of the LCD is divided into + 45 ° and −45 ° for each line by Xpol. In the case of the outgoing polarization axis (+ 45 °) 13a, the angle θa formed by the incident polarization axis 11 and the slow axis 12a of the half-wave plate is set to 0 °. In the case of the outgoing polarization axis (−45 °) 13b, the angle θb formed by the incident polarization axis 11 and the slow axis 12b of the half-wave plate is set to 45 °.
Since the purpose is to make the outgoing deflection angles for each line orthogonal to each other, there are various combinations of the values of θa and θb. The simpler would be better when considering manufacturing.

  FIG. 6 shows the relationship between the vertical position of the screen and the time for the LCD display 14, the operation 15 of the polarization axis variable liquid crystal plate 15, and the movement 16 of the LED backlight turn-off position. The vertical axis represents from the top to the bottom of the image, and the horizontal axis is the time axis. The image display time is a number that is generalized in the current system. That is, Lf and Rf are displayed at 1/120 sec, and 1 frame is 1/60 sec. That is, since there is 60 Hz display, there is no problem of flicker. The polarization axis variable liquid crystal plate does not need to have the same number of patterns as the number of lines of the image.

The number of lines shown on the right side of the display 14 on the LCD is a standard for digital high vision. That is, the total number of lines is 1115 and the effective number is 1080. Lines 1081 to 1115 are vertical blanking periods, and the image is black.
Since the stereoscopic LCD is not only used as a television receiver but also strongly conscious of the display terminal of a personal computer, the numbers written here are just reference values.

  FIG. 7 is a configuration diagram of the stereoscopic display of the present invention. That is, the LED backlight 5, LCD 6, Xpol (1/2 wavelength plate) 7, polarization axis variable liquid crystal plate 8, and ¼ wavelength plate 17 constitute a display. The linearly polarized light having a polarization axis of ± 45 ° exiting the polarization axis variable liquid crystal plate 8 is changed into right-handed and left-handed circularly polarized light by the horizontal slow axis 18 of the quarter-wave plate 17. The left and right images are separated and viewed stereoscopically with circularly polarized glasses 19.

  This display can be used for both 2D and 3D. In general, circularly polarized glasses are not required for 2D, but in the case of drawing work using a personal computer, both 2D and 3D work can be performed with circularly polarized glasses applied. This is because the vertical resolution does not change as in the prior art.

1L original image (left)
1R Original image (right)
2LR L first image 2RL R first image 3L Conventional playback image (left)
3R Conventional playback image (right)
4L New system playback image (left)
4R New system playback image (right)
5 LED backlight 6 LCD (Liquid Crystal Display)
7 Xpol (1/2 wavelength plate)
8 Polarization axis variable liquid crystal plate 9 Rf and Lf boundary 10 Polarization direction boundary 11 Polarization transmission axis of LCD = incident polarization axis 12 to Xpol Sol axis 12a for each line of Xpol (1/2 wavelength plate) Slow axis (Θ = 0 °)
12b Slow axis (θ = 45 °)
13a Output polarization axis (+ 45 °)
13b Output polarization axis (-45 °)
14 LCD display 15 Operation of polarization axis variable liquid crystal plate 16 Movement of LED backlight extinguishing area 17 1/4 wavelength plate 18 Slow axis 19 Circular polarized glasses

Claims (4)

  In a 2D / 3D liquid crystal display with a half-wave plate on the front of the LCD screen and the direction of the slow axis changed for each line, the right image of the stereo pair is assigned to odd lines and the left image is assigned to even lines Two types of images (referred to as R-first images) and left-hand images as odd lines and right-images as allocated to the arithmetic lines (referred to as L-first images). Stereoscopic display that displays alternately at frame rate.   On the front surface of the stereoscopic display, a liquid crystal plate (which is called a polarization axis variable liquid crystal plate) that changes the polarization direction consisting of a large number of horizontally long screen patterns is placed, and the R first image and the L first image are arranged. A stereoscopic display in which the polarization direction is changed by 90 ° sequentially from the top to the bottom of the screen in accordance with the rewriting position.   The rewrite position of the R-first image and L-first image and the switching position of the polarization direction of the polarization axis variable liquid crystal plate are provided, and a horizontally long extinguishing area consisting of a plurality of lines is provided. A stereoscopic display with a backlight that moves sequentially from top to bottom.   A stereoscopic display in which a quarter-wave plate is placed in front of the polarization axis variable liquid crystal plate and converted into right-handed and left-handed circularly polarized light, and left and right images are separated from each other by circularly polarized glasses that are reversely rotated.

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