Patent Application
20160212416
The present invention is in the field of autostereoscopic displays. It relates to a method of creating dynamic exit pupils according to the viewer's position, and presenting the stereo images to the viewer.
Autostereoscopic displays create virtual viewing windows, through which intended perspective images can be presented. Through these viewing windows, right and left eye of the viewer see different images, and perceive stereo image without the need of glasses. There are several different methods to create virtual viewing windows. These methods utilize parallax barrier, lenticular lenslet, Fresnel lens (pupil forming screen), retro-reflective light diffusing material, or light shaping diffuser (LSD) technology.
In parallax barrier based displays, right and left eye images are interlaced in columns on the display, typically an LCD display. A parallax barrier is positioned in front of the display so that it creates vertical viewing windows for right eye and left eye, separately. Created right and left eye viewing windows are repeated horizontally along the viewer's space. Thus, as long as the viewer's right eye is in the right eye viewing window, and left eye is in the left eye viewing window, the viewer perceives 3D. U.S. Pat. No. 6,459,532 is an example of the parallax barrier method. It must be noted that this is not the only way of parallax barrier usage.
Lenticular screens can be used as in parallax barrier case. The horizontally interlaced right and left images on the display are diffused by the lenticular screen so that right eye image pixels can be seen only in the right eye viewing windows and left eye image pixels can be seen only in the left eye viewing windows. Thus, viewer can perceive 3D as long as viewer's right and left eye are in the corresponding viewing windows. U.S. Pat. No. 6,069,650 utilizes the mentioned method.
Another usage of lenticular screens in autostereoscopic displays is based on the optical property that lenticular screens can be used to retro-reflect projected light back to the source, horizontally. U.S. Pat. No. 7,874,678 describes a lenticular lenslet based display method which utilizes the mentioned optical property. Since each single lenticule in lenticular screen focuses light in only one direction, which is horizontal direction in the mentioned patent, lenticular screen creates vertical viewing windows, in which the image projected by the corresponding projector is presented. By placing multiple projectors, which are horizontally apart from each other, not more than an average human interpupillary distance (approximately 65 mm), multiple vertical viewing windows are created in the viewer's space. Through each vertical viewing window, the perspective image projected by the corresponding projector can be seen. Thus, the viewer perceives stereo images in the viewer's space . It must be noted that instead of placing multiple projectors horizontally apart from each other, two projector could be used and horizontally move according to the position of viewer.
Another usage of lenticular screens is placing a diffuser between two lenticular screens, as in U.S. Pat. No. 5,703,717. The constructed screen is called as double lenticular screen and it is used in the rear projection displays. A projector projects image onto the double lenticular screen. The lenticular screen, in the projector side, focuses light as thin vertical stripes onto the diffuser. The lenticular screen, in the viewer side, diffuses vertical stripes on the diffuser, such that the projected image can be seen only in a narrow vertical viewing window. Thus, by placing multiple projectors horizontally apart from each other and creating multiple viewing windows, or by moving two projectors according to the position of viewer, viewer can perceive 3D.
In fresnel lens based displays, a vertical diffuser is placed onto Fresnel lens, U.S. Pat. No. 7,699,472 B2. The Fresnel lens focuses the projected image by projector, and then diffuser diffuses this focused image into a vertical viewing window. By placing multiple projectors horizontally apart from each other or by moving two projectors according to the position of viewer, viewer can perceive 3D through these created viewing windows. It must be noted that this is not the only method to make use of Fresnel lens in autostereoscopic displays.
A retro-reflective light diffusing material can also be used to create viewing slits to present stereo images as disclosed in U.S. Pat. No. 7,993,016 B2. A retro-reflective diffusing material consists of a retro-reflector sheet and a light diffusing sheet which diffuses light in one direction much more than the other directions. A retro-reflector reflects incident light back to the source. If a projector projects image onto a retro-reflector, retro-reflector forms an exit pupil at the same position as the projection lens. In order to see the projected image, the viewer must look through the created exit pupil, but it is impossible for two objects, eye of the viewer and projection lens, to occupy same position in space. By placing a vertical diffuser before the retro-reflector, exit pupil is expanded in the vertical direction. Thus, anyone looks through vertically expanded exit pupil, called vertical viewing slit, can see the projected image. By placing multiple projectors horizontally apart from each other, as in aforementioned patent, or by moving two projectors according to the position of the viewer, viewer can perceive 3D in a comfortable viewing area.
In all methods mentioned so far, except parallax barrier method, in order to present stereoscopic images to the viewer in a comfortable viewing area, either multiple projectors must be used or projectors must move according to the position of the viewer. These solutions have some drawbacks. In multiple projector method, using many projectors will cause high cost, complex system structure, and image registration problem. In the case of moving projectors, image registration problem, which is the problem of projecting images on the substantially overlapping areas of the screen, and correcting the image distortions, will occur in every movement of projectors.
Another problem with the multiple projector method and the parallax barrier method is that they create discrete viewing windows. Thus, when the viewer changes its position, viewer experiences discrete transitions between viewing windows, and it causes unnatural 3D experience. Therefore, an autostereoscopic display method, which aims to solve all aforementioned problems and presents a high quality 3D experience, is necessary.
The present invention is in the field of autostereoscopic displays. It relates to a method of forming dynamic exit pupils by a transfer screen according to the viewer's position, and presenting the stereo images to the viewer. By the present invention, the viewer perceives stereo images in a comfortable viewing field without need of any glasses, or so.
The method of the present invention is based on the forming slit shaped exit pupils according to the position of viewer. Slit shaped exit pupils will be called as viewing slits in the present invention. In autostereoscopic display literature, there are several different transfer screens which can create fixed viewing slits. A transfer screen can be thought as a special imaging system, which both images and diffuses at the same time. It images projection lens of the projector used in the display, and diffuses this image in one axis, its major diffusing axis, much more than its orthogonal axis, minor diffusing axis. Thus, it forms a slit shaped exit pupil, so called viewing slit, through which image information, projected by the projector on the transfer screen, can be observed. The formed viewing slit is parallel to the major diffusing axis of the transfer screen, it has a virtual anchor point which is anchored to the spatial position of image of projection lens and it is free to rotate around its anchor point. Some transfer screen examples are lenticular screen in front of a reflective back surface (U.S. Pat. No. 7,874,678), double lenticular screen (U.S. Pat. No. 5,703,717), single axis diffuser in front of a fresnel lens (U.S. Pat. No. 7,699,472 B2), and retro-reflective light diffusing material (U.S. Pat. No. 7,993,016 B2).
In the method of present invention, two projectors are placed apart from each other by the average human interpupillary distance, while one of projectors, right eye projector, projects right image of stereo image pair, and the other, left eye projector, projects left image of stereo image pair onto the transfer screen. The transfer screen forms two viewing slits, as mentioned in the previous paragraph. One of them is coupled with the right eye projector, and the other one is coupled with the left eye projector. Since the distance between projection lenses' of projectors is fixed to the interpupillary distance, and each formed viewing slit has the virtual anchor point which is the image of corresponding projection lens, the distance between right and left eye viewing slits is also interpupillary distance. Thus, right and left eyes of the viewer can fit into right and left eye viewing slits, respectively, and viewer perceives stereo image by looking through these viewing slits. Since the distance between projectors are fixed, changing the direction of major diffusing axis of transfer screen, that is to say the direction of viewing slits, doesn't change the distance between viewing slits along the axis on which projection lenses of projectors are aligned. This permits to change the direction of major diffusing axis, that is to say the direction of viewing slits, and create viewing slits according to the position of the viewer. In the present invention, a head-tracker unit (H) locates the position of viewer's eyes, a mechanical unit (M) rotates the transfer screen around its center, according to the position information of viewer's eyes, such that right and left eye viewing slits are also rotated around virtual anchor points and formed on the right and left eye of the viewer, respectively. Thus, viewing slits dynamically track the viewer (460) in a large viewing field (880), and the viewer perceives stereo images without need of wearing any glasses, or so.
The present invention has advantages over conventional autostereoscopic projection displays in terms of number of projectors, transition between different perspectives, and the image registration on the screen. The present invention employs two projectors rather than an array of projectors, which decreases the cost, and complexity of the display. In the present invention, there is no loss of 3D vision and discrete transition between different perspectives when the viewer changes his position. In the present invention, since neither projectors nor screen make translational movement, projected images are always overlapped on the screen, and no distortion correction is required.
The reference numbers as used in figures possess the following meanings;
The present invention is in the field of autostereoscopic displays. It relates to a method of forming dynamic exit pupils (325) by a transfer screen (320) according to the viewer's position, and presenting the stereo images to the viewer. By the present invention, the viewer perceives stereo images in a comfortable viewing field (990) without need of any glasses, or so.
In order to understand the present invention, one must know how an exit pupil (325), so called viewing slit (325), is formed by a transfer screen (320), and what properties it has. Thus, in this section, the formation of viewing slits by the transfer screen (320) will be explained. In the next section, the present invention will be explained according to a preferred embodiment.
Autostereoscopic displays control light path such that they create viewing slits (325), through which different perspectives of the stereo image are observed, in different spatial positions. There are several different ways to control light path for autostereoscopic displays. One of them is relaying the projected image onto a slit shaped exit pupil (325), by a transfer screen (320) which both diffuses in a single axis and images at the same time. The transfer screen (320) examples can be seen in Patents U.S. Pat. No. 7,874,678, and U.S. Pat. No. 7,993,016B2. The transfer screen (320) can be though as a special imaging system which consists of a single axis light diffuser (120) and an imaging lens (220).
In the preferred embodiment, two projectors (440R, 440L) are placed apart from each other by interpupillary distance, d, as in
In the preferred embodiment, the transfer screen (320) is a special imaging system which can relay projected images by projectors (440R, 440L) onto slit shaped exit pupils (325R, 325L), as explained through
The mechanical unit (M), in the preferred embodiment, is any system which rotates the transfer screen (320) around its center. The mechanical unit (M) can be a servo motor which is connected to transfer screen (320) either by the transfer screen's center, or by gears surrounding the transfer screen (320).
In the preferred embodiment, the head-tracker unit (H) locates eyes of the viewer (460R, 460L), and feeds the position information of viewer's eyes (460R, 460L) to the control electronics (C). The control electronics (C) calculates the angular position of eyes (460R, 460L) relative to the position of projectors (445R, 445L). The calculation of the angular position will be examined through
After the calculation of angle, a, between reference axis (770) and projector-eye axis (780), the mechanical unit (M) rotates the transfer screen (320) around its center, such that the angle between major diffusing axis (110) of transfer screen (320) and reference axis (770), is also angle of a. Thus, as seen in
In the preferred embodiment, locating the position of viewer's eyes (460R, 460L), and rotating the transfer screen (320), according to the position of viewer (460), are done in real time. Thus, viewing slits (325R, 325L) dynamically track the eyes of the viewer (460R, 460L), and the viewer (460) perceives stereo images without wearing any glasses, or so, in a large viewing field (990), as illustrated in
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2013/056842 | 8/23/2013 | WO | 00 |
