DE19500699A1 - Personal adaptive stereoscopic picture screen (PASS) - Google Patents

Abstract

The PASS consists of a cylindrical raster disc (1) and a LCD , esp. TFT display screen. The single colour pixels (7) are arranged in lines above each other. The disc is an electronically controlled shadow line LCD. The individual non-transparent vertical shadow beams (4) are independent of each other. They are switched on and off in small steps electronically. Hence the beams for the right eye of the viewer are covered by the odd number vertical pixel beams and for the left eye with the even number beams. The PASS system adapts within a certain region as far as horizontal and distance positions are concerned without the disc being moved. Hence the viewer finds himself in the correct position relative to the pixel distance on the screen (2).

Description

An autostereoscopic screen has compared to other methods, such as the shutter principle or Polarization principle has the advantage that the user does not need glasses. Becomes a prismatic stereoscopic glass in front of the picture is not mechanically adapted to the viewer position, so go Stereo effects generated by moving the viewing direction are lost. That is why in this As an alternative to the micromechanical solution, an electronic contribution is also presented, which With a view to future high-definition television: from the broadcaster or controlled by the viewer. can be a person-adaptive stereoscope or a high-resolution the (HDTV) mode can be set for all viewing directions.

The autostereoscopic usage remains limited to one person per screen, though but does not hinder collective stereoscopic use, e.g. B. with additional Ver Application of the shutter principle with glasses. The main short-term applications is in medical technology. Here, the reference to a person is not a disadvantage; anyway, only one person assesses a 3D CT image: the doctor, the annoying glasses and must avoid restricted fields of vision. If several doctors are working at the same time, you can multiple screens can be used. At the same time an auditorium wants a mikrochir Follow urgent surgery stereoscopically, this can be done using a projection method e.g. B. circularly polarized light.

Stereoscopic television will also be in a future digital television system Have space because it simply comes closest to natural viewing habits and can optionally be used if the digital coding is added during transmission provides information for the third dimension. But even today you could without much addition stereoscopic test shipments are made - by arrangement between Program channels, the right picture and the left picture being sent in one channel would. If there is no stereoscopic recording available, "Quasi HDTV "rehearsed fully compatible with today's broadcasting technology over two PAL channels will. In the home, "at the consumer", can be retrofitted for existing 100 Hz television stereoscopic representations are used according to the shutter principle [4]. If cheaper flat screens will be on the market, the upgrade is with one PASS addition obvious. The interested customer, like his PC today, will be tomorrow also have his autostereoscopic television; it offers the greatest possible naturalness 3D display without annoying aids.

After all, this is the area of flight simulation and investment today -navigation to name as a field of application, since here only 1 person is the target subject anyway is.

STATE OF THE ART

Stereoscopic film and projection processes have been in use for years Commitment. Mostly polarized light (horizontal / vertical, circular) is used to the right and separate left image. With the advancement of LCD technology, it became possible Control the light transmission of crystals electronically. This made the development of the Shutter technology possible, with the right one alternating with the field frequency and the left lens becomes opaque and synchronized right and left pictures  appear sequentially on the screen [4].

Autostereoscopic projections are made with the help of screens with stripe lens grids performed several directions of projection. The corresponding direction is the correct perspective image assigned [2]. A smooth transition from one perspective to another The next one can hardly be reached because the number of projection directions is not arbitrary can be increased. With an autostereoscopic display that is intended for only one person is, you only use two perspectives that require a certain direction of view [3], [8th]. A fully stereoscopic illusion world is achieved using "Head Mounted Displays", which are supplied by powerful VR computers (Virtual Reality) be controlled. The exact head position and movement is detected and the associated images are generated at the same time. Of course, these are elaborate and VR systems need getting used to only for special applications.

In medical technology, magnetic resonance and computed tomography are the most important Areas of application for stereoscopic 3D visualizations. About certain perspectives you are looking for powerful special computers for "Volume Tracing Algorithms" developed [5], [6]. Combined computer visualizations and real-time transmissions from Endoscopes are becoming one of the most important neurosurgical tools. Stereoscopes Endoscopes are already in use. An electronic motion control over one Infrared based "head tracking sensor" will be easy to combine with a personal autostereoscopic screen system.

PROBLEM POSITION

In order to be able to generate a natural stereoscopic display, The following three tasks have to be solved:

• 1. The autostereoscopic screen must have the stereo effect when the head moves Maintain viewer.
• 2. A displayed object must be in the same virtual position when the head moves stay in the room (in front of and behind the screen level) so that a viewer can get involved can view the displayed object from several directions.
• 3. The head position of a viewer must be exact (without disruptive measures) must be detected and at the same time those belonging to the changed viewing direction must be detected Right and left perspectives of a 3D image calculated, read out or over a controllable camera system are included.

Hardware components are available for the 2nd and 3rd. Only suitable softwa re-solutions are developed. For 1. an arrangement with a micromechanical trackable lenticular lens proposed in front of a flat display [10].

PRINCIPLE OF THE INVENTION

The principle of the autostereoscopic screen is known Lich on that due to prism or lenticular vertical stripes in double Pixel spacing on the glass in front of the flat screen the right eye only all even pixels in a row and the left eye only sees all odd pixels (or vice versa). With the right pixel control, each eye can have its own picture  are transmitted independently - a total of one stereoscopic image. This is limited not on black and white representations, but works for all three in one pixel controlled color dots (usually RGB). However, it must be ensured here that the three color dots on top of each other and not - as is unfortunately often the case - horizontally or lie next to each other in a triangle shape, otherwise color falsifications cannot be controlled may occur.

If the position of the eyes changes in front of the screen, then either the point position (cf. [1]) must be adapted electronically or the grid must be mechanically adjusted relative to the pixel. The electronic tracking of the color image points requires the new development of high-precision electron beam picture tubes that no longer use shadow masks. However, the adaptation of the disc ( 1 ) appears to be more cost-effective, especially since, as will be shown later, a micromechanical as well as a purely electronic solution has also been found for this. If not only the horizontal position of the eyes is changed, but also the viewing distance, the optimal stereoscopic view can also be set automatically - by minimally precise adjustment of the grid glass distance.

Solutions that require mechanical movements are generally more prone to failure. Therefore forms the development of a line shadow grid LCD with a purely electronic one Position adaptation an arrangement that is also attractive for larger series; she also has that The advantage that it can alternatively be switched to non-stereoscopic high-resolution images can be. These are then independent of the viewing direction. At the Switching to the high-resolution 2D mode are simply those generated in the LCD Shadow grid switched off. In addition, the colors arranged in the offset grid have pixel of the image has the advantage that, when properly controlled with 2D images, it is almost the same provide double resolution in the vertical and horizontal directions [9]. That is, one PASS screen can probably be used for autostereoscopes as well as for HDTV applications be set. A flexible, broad product design also allows this principle: Will the correct high resolution screen, or the right display used, allows electronic adaptation also retrofits to stereo capability, in which the line shadow raster-LCD together with the position sensor in front of it.

Infrared head tracking systems are suitable as position detectors Have the required precision, but inexpensive ultrasound systems are also used bar. If you also want to detect the vertical position and the viewing distance, then so it is recommended to use at least two sensor fields. However, CCD Cameras with fast image analysis can be used. Ultrasound measurements are particularly easy if the transmitter is attached to the viewer's head may.

As Figure 2 shows, the two image perspectives can be projected onto a screen by two projectors via overhead displays, so that left and right picture elements appear alternately side by side. The distance between the lenticular screen ( 3 ) and screen ( 2 ) can be used to change the horizontal extent of a picture element - up to linear elements if the focal point of the lens is selected as the projection plane. If, as shown in Figure 3, there should also be a half-line height offset between right and left image elements, this can be done using the projection adjustment. If a horizontally extending prism or lens structure is additionally superimposed on the lens grid on the pane ( 3 ), lines can also be concentrated on the projection surface in order to generate the picture element shown in picture 3.

In the micromechanical tracking of the prismatic lens ( 1 ), slight changes in the distance position of the viewer are tolerated without changing the depth of the prismatic lens when the image elements are concentrated on the smallest possible area via the cylindrical lenses.

If the disc ( 1 ) consists of an electronically controllable line shadow raster LCD, the PASS system can adapt to horizon and distance positions within a specified range without the disc ( 1 ) having to be moved. Starting from the ideal position of the viewer, the shadow bars can be adjusted so that the stereo effect remains unchanged when the viewer moves. The ideal distance should be selected so that the viewer is at his resolution limit with regard to the pixel distance on the screen ( 2 ), ie the viewer is no longer supposed to notice the bar structure. This is the distance b (e.g. 1500 mm) in front of the screen with a horizontal pitch distance p of the picture elements on the screen (e.g. p = 0.25 mm). If the base distance of the eyes is designated a (e.g. a = 75 mm), the LCD disc ( 1 ) is attached at the following distance d from the screen ( 2 ): d = bp / a (e.g. d = 1500 _* 0.25 / 75 mm = 5 mm). The bars of the LCD can then have a width of 0.3 or 0.2 mm, for example, while the translucent slots between the bars have a width of 0.2 mm. These distances can be realized if the line shadow LCD has densely located (opaque) bars that can be switched on and off and have the smallest width of 0.1 mm. If the picture elements are projected almost linearly on the screen over the cylindrical lens disc ( 3 ), the bars can be adapted to the observer position in such a way that for every distance position of the observer between 1.5 m and 2 m the right eye only all even-numbered pixels and the left eye only sees all odd pixels completely.

When using a TFT display in which the picture elements adjoin each other and have the same brightness horizontally over the distance p, part of the light output is also lost for one eye, since the translucent strip on the pane ( 1 ) should be somewhat smaller than the pixel width in order to keep a certain margin for distance adaptation as a reserve. It is important, however, that all permeable stripes have the same width, while the black stripes may vary slightly according to the viewer's position. The smaller the uniformly large translucent strip width, the larger the adaptation range for the distance. For example, with a stripe width of only 0.1 mm and a picture element distance on the TFT display of 0.25 mm, a viewing distance range of 1 to 3 m can be adjusted to a maximum without making mechanical adjustments to the panes.

With an autostereoscopic projection screen according to Figure 2, it should be noted that the cylindrical lens structure ( 3 ) and cylindrical prism structure ( 1 ) are also interchangeable. However, the solution given here is more favorable because of a mechanical movement tolerance in the case of disc ( 1 ). The triangular structure of the prisms in ( 1 ) is also not mandatory: a cylindrical lens structure can also be used in ( 1 ) if the focal point does not only fall on the projection layer but behind it.

With regard to Figures 1 and 2, it should be noted that they are not drawn in proportion to the actual arrangement, but only to illustrate the principle, with larger grid spacings. The number of points is also between 500 and 2000 per image.

literature

[1] S.Hemschke: stereoscopic screen. Patent application P 4114 023.0 (1991).

[2] R. Börner: Autostereoscopic 3-D imaging by front and rear projection and on Fiat Panel displays. Displays, Vol. 14, No. 1 (1993), pp. 39-46.

[3] Sheat D E, Chamberlin G R, Gentry P, Leggat JS, McCartney DJ: 3-D Imaging Systems for Telecommunications Applications. Proc. SPIE, vol. 1669, p. 186. Electronic Imaging Systems and Applications Meeting, San Jose (1992).

[4] S.Hemschke, A.Herrfeld, C.Junge, R. Kothe: Stereoscopes real-time image processing. CeBIT exhibit and brochure (1994).

[5] H. P. Mainzer, K. Meetz, D. Scheppelmann, U. Engelmann, H. J. Bauer: The Heidelberg Ray tracing model. IEEE Computer Graphics and Appl. Nov. 1991 pp. 34ff.

[6] J. Lichtermann, G. Mittelhäußer: A hardware architecture for real-time visualization Volume data through "Direct Volume Rendering". Workshop visualization tion techniques Stuttgart (1991).

[7] S. Hentschke: Personal autostereoscopic screen. Patent application P 44 33 058.8 (1994).

[8] R. Börner: Autostereoskope rear projection and flat screens. TV and Kinotechnik Vol. 48, No. 11 (1994). S.594-600.

[9] B. Wendland: Concepts for a compatible HiFi television system. NTG technical reports 74. (1980) pp. 325-334.

[10] R. Börner: playback device for three-dimensional perception of images. Autostereoscopic Viewing Device for Creating Three Dimensional Perception of Images. German Patent No. DE 39 21 061-A1. (Note 1989).

Claims (9)

1. Person-adaptive stereoscopic screen (PASS), consisting of a cylindrical screen ( 1 ) and a screen ( 2 ), characterized in that the screen ( 2 ) is an LCD display (in particular a TFT), in which the individual NEN (color ) Picture elements ( 7 ) are arranged in columns one above the other, and that the cylinder grid disc ( 1 ) is an electronically controllable shadow line LCD, in which the individual opaque vertical shadow bars ( 4 ) in width and position independently of one another in small steps ( 8 ) can be switched on and off electronically, so that a bar for the right eye of a viewer, the vertical pixel columns with odd numbers and for the left, the picture element columns (pixel columns) are covered with even numbers (see Fig . 1). 2. Person-adaptive stereoscopic screen (PASS), consisting of a cylindrical screen ( 1 ) and a screen ( 2 ), in which on all odd pixel columns the elements of the left image perspective and on all even ones that appear the right image perspective, characterized in that accordingly the horizontal and distance position of the viewer in front of the screen, which is detected with an optical or acoustic sensor system attached to the edge of the screen and a control signal is generated therefrom, which slightly adjusts the bar grid ( 4 ) of the pane ( 1 ) so that the optimal stereoscopic view is maintained when moving the viewer in the definition area. 3. Person-adaptive stereoscopic screen (PASS) according to claim 1 or 2, characterized in that with a real time computer that of the horizontal  Position of the viewer and gff. also that of the detected vertical and distance positions tion corresponding right and left images of a 3-D image information is calculated and put on the stereo screen. 4. person-adaptive stereoscopic screen according to claim 1 and 2, characterized in that the pixels of the right image are vertically shifted by half a pixel pitch compared to those of the left and the shadow bar of the LCD ( 1 ) can be switched off completely, so that instead of one stereoscopic image, a high-resolution 2D image can be displayed (see Figure 3). 5. person-adaptive stereoscopic screen (PASS) according to claim 2, 3 or 4, characterized in that the right and left images on ( 2 ) via a cylindrical lens screen ( 3 ) of two projectors, one of which is the right and the other the left image supplies, are projected onto the screen ( 2 ), so that right and left picture elements alternate horizontally (see Fig . 2). 6. person-adaptive stereoscopic screen (PASS) according to claim 5, characterized in that the grid with vertical cylindrical lenses a grid of horizontal cylinder prisms triangular cf. Fig. 2) is superimposed with the line pitch spacing, so that a line is concentrated to half the pitch height and right and left pixels appear half a line apart, due to the fact that the two projectors have a slightly different height position (see Fig . 3). 7. person-adaptive stereoscopic screen (PASS) according to claim 5, or 6, characterized in that the grid disc ( 1 ) has no bars, but a prismatic grid structure or also a cylindrical lens structure (with vertical cylinders) with about a pitch distance of two picture elements and that these The disc is micromechanically adapted horizontally and possibly also at a distance from the image disc ( 2 ) to the position of the viewer, so that the stereo effect from the different positions is retained for the viewer (see Fig . 2). 8. Person-adaptive stereoscopic screen (PASS) according to claim 7, characterized in that conversely the projection screen ( 3 ) has a prism and the front disk ( 1 ) has a cylindrical lens structure. 9. person-adaptive stereoscopic screen according to claim 1, 2 or 3, characterized in that the distance of the prism grid from the lens grid glass (see Fig . 1) can be reset to a minimum for a switch from stereoscopes to a high-resolution 2-D mode .