KR102659822B1 - Transparent cylindrical 3D display system using holographic optical element - Google Patents

Abstract

The present invention relates to a three-dimensional display system, comprising a display module and a projector module, wherein the display module includes a scanning mirror that rotates by a motor and reflects light based on a three-dimensional image incident from the projector module; And a holographic diffuser that surrounds the scanning mirror, is provided so that the scanning mirror located inside can rotate, and provides a three-dimensional image to the viewer by changing the path of light reflected from the scanning mirror. . This allows the scanning mirror to position a 3D virtual image within the cylinder without blocking the external background, thereby providing the external background and virtual image to the viewer at the same time.

Description

Transparent cylindrical 3D display system using holographic optical element}

The present invention relates to a transparent cylindrical three-dimensional display system using a holographic optical element, and more specifically, to a transparent cylindrical three-dimensional display system using a holographic optical element that can be viewed from all directions.

Recently, as 3D display technology has developed, objects can be expressed with perfect parallax and depth, eliminating the symptoms of eye fatigue and dizziness caused by the accommodation-convergence mismatch problem. Furthermore, holographic display technology has developed into the ultimate three-dimensional display technology that allows viewing different images depending on the movement of the viewpoint and allows multiple viewing without the need for additional devices (e.g. glasses) for viewing. did.

Additionally, research is being actively conducted on Light Field Display, a display technology that reproduces the light field, which is the distribution of rays existing in space, into the viewer's space.

As shown in FIG. 1, the conventional cylindrical 3D display device using this 3D display technology consists of an anisotropic diffusion plate 10 and a high-speed projector 20 attached to a scanning mirror rotated by a motor M. there is. And when the high-speed projector 20, which is synchronized with the rotation angle of the anisotropic diffusion plate 10 attached to the rotating scanning mirror, forms a viewpoint that provides a three-dimensional image, the image formed through time division driving is displayed in the view volume (view). volume) and provide 3D images to viewers.

However, in this case, there is a problem that the external background is obscured by the scanning mirror to which the anisotropic diffusion plate 10 is attached, so the viewer views only the three-dimensional virtual image without being able to see the background.

Korean Patent Publication No. 10-2006-0081112

The present invention was devised to solve the above problems, and the purpose of the present invention is to provide a transparent cylindrical three-dimensional display system that can simultaneously provide the external background and a virtual image to the viewer without the scanning mirror blocking the external background. will be.

A three-dimensional display system according to an embodiment of the present invention for achieving the above object is a three-dimensional display system including a display module and a projector module, where the display module rotates by a motor and transmits light incident from the projector module. a scanning mirror that reflects light based on a three-dimensional image; And a holographic diffuser that surrounds the scanning mirror, is provided so that the scanning mirror located inside can rotate, and provides a three-dimensional image to the viewer by changing the path of light reflected from the scanning mirror. .

Here, the holographic diffuser uses a holographic optical element (HOE) as a medium to generate diffraction only at specific wavelengths of light, and passes wavelengths other than the specific wavelength to display the three-dimensional image and the external background together. It may be a see-through type provided.

And the projector module includes a plurality of light sources that irradiate light containing the specific wavelength; a fiber combiner combining light emitted from the plurality of light sources; a collimator that converts the combined light through the fiber combiner into parallel light; A spatial light modulator (SLM) that restores pre-stored holographic data into the three-dimensional image; a projection lens that transmits the 3D image restored by the spatial light modulator to the scanning mirror; and a TIR (Total Internal Refraction) prism located between the spatial light modulator and the projection lens to cause the parallel light to enter the spatial light modulator and to transmit the three-dimensional image restored from the spatial light modulator to the projection lens. It can be included.

Additionally, the projector module may transmit a three-dimensional image corresponding to the rotation angle of the scanning mirror to the scanning mirror based on the rotation speed of the scanning mirror.

In addition, the holographic diffuser can provide different images depending on the viewpoint by forming a 360-degree multiple viewpoint by setting the vertical and horizontal diffusion angles differently.

Additionally, the holographic diffuser may be cylindrical, and its inner diameter may be larger than the outer diameter of the scanning mirror.

According to one aspect of the present invention described above, by providing a transparent cylindrical three-dimensional display system using a holographic optical element according to an embodiment of the present invention, a three-dimensional virtual image is located within the cylinder without the scanning mirror blocking the external background. By doing so, the external background and virtual image can be provided to the viewer at the same time.

1 is a schematic diagram of a conventional three-dimensional display without an external background;
2 to 4 are diagrams for explaining the configuration of a three-dimensional display system according to this embodiment;
5 to 8 are diagrams for explaining how a 3D image is provided by the 3D display system according to the present embodiment, and
Figures 9 and 10 are diagrams to explain how an external background and a 3D image are provided to a viewer together according to the 3D display system according to this embodiment.

The detailed description of the present invention described below refers to the accompanying drawings, which show by way of example specific embodiments in which the present invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It should be understood that the various embodiments of the present invention are different from one another but are not necessarily mutually exclusive. For example, specific shapes, structures and characteristics described herein may be implemented in one embodiment without departing from the spirit and scope of the invention. Additionally, it should be understood that the location or arrangement of individual components within each disclosed embodiment may be changed without departing from the spirit and scope of the invention. Accordingly, the detailed description that follows is not intended to be taken in a limiting sense, and the scope of the invention is limited only by the appended claims, together with all equivalents to what those claims assert, if properly described. Similar reference numbers in the drawings refer to identical or similar functions across various aspects.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the drawings.

2 to 4 are schematic diagrams for explaining the configuration of a 3D display system according to this embodiment.

The 3D display system 1 according to this embodiment is provided to provide a see-through 3D display that can provide the viewer with a 3D image and an external background.

To this end, the 3D display system 1 may include a display module 100, a projector module 200, and a fixing module 300.

The display module 100 is provided to allow viewers to watch 3D images by playing back preset 3D images. As shown, the display module 100 is located at the top of the upper frame 330, It may include a motor (M), a scanning mirror 110, and a holographic diffuser 120.

The motor M is connected to the scanning mirror 110 and is provided to rotate the scanning mirror 110, and may be fixed by the second fixing part 340.

One side of the scanning mirror 110 is connected to a motor M so as to be rotatable by the motor M, and can reflect light based on a three-dimensional image incident from the projector module 200.

The holographic diffuser 120 surrounds the scanning mirror 110, and may be provided in a size such that the scanning mirror 110 located inside can be rotated by the motor M, and is located at the bottom of the holographic diffuser 120. It can be fixed on the upper frame 330 by inserting the third fixing part 350 located on the upper frame 330, and the holographic diffuser 120 and the third fixing part 350 are fitted and coupled. It can be fixed by screw connection.

This holographic diffuser 120 is provided to allow viewers to view a three-dimensional image by changing the path of light incident from the projector module 200 and reflected from the scanning mirror 110. As shown in the drawing, the holographic diffuser has a cylindrical shape. It is formed to surround the scanning mirror 110, and a three-dimensional image can be located inside the cylindrical holographic diffuser 120.

And the holographic diffuser 120 uses a holographic optical element (HOE) as a medium, so that diffraction occurs only at specific wavelengths of light and allows wavelengths other than the specific wavelength to pass. That is, since the holographic diffuser 120 according to this embodiment has wavelength selectivity, diffraction occurs only at the wavelength of light used in the light source 210 included in the projector module 200, and the wavelength of light irradiated from the light source 210 is By allowing wavelengths other than these to pass through, the holographic diffuser 120 appears transparent. Therefore, it can be provided as a see-through that provides both a 3D image and an external background.

Accordingly, the holographic diffuser 120 is provided in a cylindrical shape, so that as the scanning mirror 110 rotates, the three-dimensional image emitted from the projector module 200 is scanned, forming a 360-degree viewing area. In addition, the inner diameter of the holographic diffuser 120 is larger than the outer diameter of the scanning mirror 110, so that the scanning mirror 110 can be rotated by a motor inside the holographic diffuser 120.

In addition, since the holographic diffuser 120 of the present invention is provided in a cylindrical shape, two characteristics are required. One is that the angle of light diffused from the screen must be limited to form a horizontal parallax in the form of a cylinder, and the other is that the angle of light diffused from the screen must be limited to form a horizontal parallax in the form of a cylinder. The diffusion angle must be large to improve the viewing angle.

Accordingly, the holographic diffuser 120 can provide different images depending on the viewpoint by forming a 360-degree multiple viewpoint by setting the vertical and horizontal diffusion angles differently.

The vertical diffusion angle and horizontal diffusion angle can be used to obtain the angle between viewpoints based on the number of time-sharing projectors and the number of viewpoints to be formed, the viewing distance such as the viewer and the holographic diffuser 120, and the lens viewing angle (AFOV, Angular Field of View), it is possible to derive the vertical diffusion angle, horizontal diffusion angle, and view volume based on the viewpoint interval. This will be explained with reference to FIGS. 5 to 8.

The holographic diffuser 120 according to the present invention can diffuse light at a wide angle in the vertical direction of the viewer and diffuse light at a narrow angle in the horizontal direction, thereby providing binocular parallax to the viewer. .

Accordingly, the 3D image transmitted from the projector module 200 is projected onto the holographic diffuser 120 through the rotating scanning mirror 110, and the light reaching the holographic diffuser 120 is bent, so the light path is changed and the viewer Since it can be reached, viewers can receive three-dimensional images.

Meanwhile, the projector module 200 is provided to transmit the restored 3D image to the display module 100 so that the 3D image can be provided to the viewer. As shown, the lower frame 310 and the upper frame It can be arranged between (330). And the projector module 200 includes a light source 210, a fiber combiner 220, a collimator 230, a spatial light modulator 250, a projection lens 260, and a Total Internal Refraction (TIR) prism 240. can do.

The light source 210 is provided to irradiate light containing a specific wavelength. It operates at a single wavelength to generate and express a monochromatic three-dimensional image, or operates at different wavelengths to generate and express a multicolor three-dimensional image. It can operate at wavelengths.

The light source 210 of the present invention is provided in plural, and here, the specific wavelength may be a wavelength that allows diffraction to occur in the holographic optical element that is the medium of the holographic diffuser 120, and in the present invention, the wavelength is 120 mW/cm2. A plurality of light sources 210 capable of irradiating RGB laser light with wavelengths of 520 nm and 638 nm, respectively, are set as output, but the light source is not limited thereto. Additionally, the light source 210 may be fixedly positioned at the bottom of the upper frame 330 adjacent to the projection lens 260.

The fiber combiner 220 is provided to combine the respective lights emitted from the plurality of light sources 210, and as shown in the drawing, it is fixed to the bottom of the upper frame 330 adjacent to the projection lens 260. can be located

Meanwhile, the collimator 230 is located on the path of the combined light through the fiber combiner 220, converts the combined light into parallel light, and is provided to change the optical path so that the parallel light faces the TIR prism 240. It can be provided in a fixed state at the top of the lower frame 310.

A spatial light modulator (SLM, Spatial Light Modulator) is provided to restore pre-stored hologram data into a three-dimensional image provided to viewers, and parallel light with a changed optical path is incident through the TIR prism 240.

This spatial light modulator 250 is a micro display device and may be a DMD (Digital Micromirror Device) with high resolution, small pixel size, and high frame rate, and thus the space of parallel light incident through the TIR prism 240 Hologram data can be restored into a 3D image by performing modulation.

Additionally, the spatial light modulator 250 may be provided to be fixed on the lower frame 310 adjacent to the collimator 230 as shown in the drawing.

Meanwhile, the projection lens 260 can transmit the 3D image restored from the spatial light modulator to the display module 100 including the scanning mirror 110. This projection lens 260 may include an adjustable optical aperture, which adjusts the depth of field. This is to solve the problem that the 3D image restored by the spatial light modulator 250 according to the present embodiment is tilted toward the holographic diffuser 120 and the image is distorted. In the present invention, as shown in FIG. 8, a projection lens ( 260)'s depth of field was improved.

Additionally, the projection lens 260 may be located at the top of the TIR prism 240, but may be located at the bottom center of the upper frame 330 to transmit a 3D image to the display module 100.

The TIR (Total Internal Refraction) prism 240 is located between the spatial light modulator 250 and the projection lens 260 so that the parallel light transmitted from the collimator 230 is incident on the spatial light modulator 250, and the spatial light The 3D image restored by the modulator 250 can be transmitted to the projection lens 260.

Although not shown in the drawing, the three-dimensional display system including the projector module 200 displays the scanning mirror 110 based on the rotation speed of the scanning mirror 110 through a control unit (not shown) or a control device (not shown). A 3D image corresponding to the rotation angle can be restored in the spatial light modulator 250 and transmitted to the scanning mirror 110.

When the 3D image restored in the projector module 200 is transmitted to the display module 100, the 3D image may be transmitted to the transparent cylindrical holographic diffuser 120 through the scanning mirror 110. Afterwards, the path of the light incident on the holographic diffuser 120 is changed so that the light of the 3D image reaches the viewer, allowing the viewer to see not only the 3D image but also the external background beyond the transparent cylindrical holographic diffuser 120. do.

Meanwhile, the fixing module 300 is provided to fix the display module 100 and the projector module 200 constituting the three-dimensional display system 1, and includes the lower frame 310, the first fixing part, and the upper frame 330. ), and may include a second fixing part 340 and a third fixing part 350.

The lower frame 310 is located at the bottom and is provided to fix the projector module 200, and is shown in the drawing as having a circular shape, but is not limited thereto.

The first fixing part 320 may be provided with a plurality of pillars as shown, and is provided to provide a space where the projector module 200 can be located between the lower frame 310 and the upper frame 330. do. Accordingly, one side of the first fixing part 320 may be connected to the lower frame 310 and the other side may be connected to the upper frame 330. The height of the first fixing part 320 is the sum of the heights of the projection lens 260, the TIR prism 240, and the spatial light modulator 250 located on the central axis of the upper frame 330, and the height of the viewer is 3D. It can be prepared based on the height at which images can be provided.

The upper frame 330 is provided to secure the display module 100 on the projection module 200, and may be connected to the other side of the first fixing part 320 and positioned at a certain height from the ground. Like the lower frame 310, the upper frame 330 may also be provided in a shape other than circular.

The second fixing part 340 is provided to fix the motor (M) and the scanning mirror 110 connected to the motor (M). One end is fixed to the upper frame 330 and the other end fixes the motor (M). can do. At this time, the second fixing part 340 may further include a separate component for reducing shaking or vibration of the display module 100 and the projector module 200 due to the driving of the motor M.

Meanwhile, the third fixing part 350 is coupled with the holographic diffuser 120 and is provided to fix the holographic diffuser 120 on the upper frame 330, and is provided at a predetermined height from the top of the upper frame 330. It may be provided to be inserted into the interior of the holographic diffuser 120 by protruding as much as possible. The diameter of the third fixing part 350 is the same as the inner diameter of the holographic diffuser 120 or is larger than the inner diameter of the holographic diffuser 120, so that the holographic diffuser 120 is damaged by external pressure unintended by the user. Separation from the upper frame 330 can be prevented.

Meanwhile, FIGS. 5 to 8 are diagrams to explain how a 3D image is provided by the transparent cylindrical 3D display system 1 according to this embodiment.

The projector modules 200 shown in FIG. 5 are virtual rotating projector modules 200 by the rotating scanning mirror 110. That is, information on a specific angle among the 3D images transmitted from the projector module 200 based on the rotation speed of the scanning mirror 110 may be part of one viewpoint. The implemented viewpoints provide binocular parallax effects and motion parallax effects to viewers, allowing them to perceive 3D images.

That is, as shown in FIG. 6, when light emitted from the light source 210 is incident on the spatial light modulator 250 through the TIR prism 240, the three-dimensional image restored by the spatial light modulator 250 is returned to the TIR prism. A three-dimensional image is displayed in the holographic diffuser 120 through 240 and projection lens 260. At this time, the viewer can see the external background along with the 3D image as shown in the drawing.

At this time, as described above, if the horizontal diffusion angle on the surface of the holographic diffuser 120 is too large, the 3D image appears blurred, and if the diffusion angle is too small, a black line appears in the 3D image. According to this embodiment, 3 The dimensional display system 1 makes it possible to specify appropriate horizontal and vertical diffusion angles.

Figure 7 (a) shows the vertical diffusion angle ( ), and (b) in Figure 7 is a conceptual diagram for calculating the horizontal diffusion angle ( ) As a conceptual diagram for obtaining, in the following, the number of time-sharing projectors is set to 512 and 512 viewpoints are to be formed. The viewing distance between the viewer and the 3D display system (1) is set to 512 for the viewer to observe all virtual objects. The distance can be selected as a minimum of 20cm, and the lens viewing angle (AFOV) can be selected as 14.4 degrees, which is the same as the viewing angle of the projection lens 260.

And the view volume of this 3D display system 1 can be calculated through the following equations.

The horizontal and vertical diffusion angles of the screen are respectively and In this case, N, the number of viewpoints of the display, is determined as shown in Equation 1 below.

[Equation 1]

And when the minimum viewing distance is d according to the vertical diffusion angle, the height w of the screen can be equal to Equation 2 below.

[Equation 2]

Additionally, in this embodiment, since the view volume, which is the area where the viewer can view the 3D image, is created in the shape of a cylinder, the radius of the cylinder, R, is the viewing angle of the projection lens, AFOC, and the distance between the projection lens and the center of the system. It can be determined by Equation 3 below.

[Equation 3]

Meanwhile, since the height of the view volume matches the height of the screen, the volume V of the view volume is equal to Equation 4 below.

[Equation 4]

In the example, the horizontal diffusion angle is about 0.7 degrees, so the number of viewpoints N is set to 512, the vertical diffusion angle is 22.6 degrees, the vertical length (w) is 95 mm, Since is 195mm, the view volume was derived to be approximately 64.3mL.

9 and 10 are diagrams to explain how an external background and a 3D image are provided to a viewer together according to the transparent cylindrical 3D display system 1 according to this embodiment. This figure is the result of an experiment based on the case where the resolution of the spatial light modulator 250 is 1,024x768, the switching speed is 22,727Hz, the maximum speed of the motor (M) is 3,070rpm, and the encoder resolution is 512 per cycle.

The drawing is the result of installing a camera at a distance of 20 cm from the holographic diffuser 120 on behalf of the viewer and rotating 360 degrees around the holographic diffuser 120 to obtain an image. FIGS. 9 (a) and 10 (a) are rendering images, and FIGS. 9 (b) and 10 (b) are projection images implemented with the 3D display system 1 of the present invention. And Figure 9 is the result of shooting in a room with a dark background, and Figure 10 is the result of shooting when there is text as an external background.

As can be seen through FIGS. 9 and 10, the 3D display system 1 according to this embodiment can not only provide a 3D image and text as an external background to the viewer, but also provide a three-dimensional effect by implementing horizontal parallax. You can see that it is possible.

The components according to the present invention are components defined by functional division rather than physical division, and can be defined by the functions each performs. Each component may be implemented as hardware or program code and processing units that perform each function, and the functions of two or more components may be included and implemented in one component. Therefore, the names given to the components in the following embodiments are not intended to physically distinguish each component, but are given to suggest the representative function performed by each component, and the names of the components are used to describe the present invention. It should be noted that the technical idea is not limited.

Although various embodiments of the present invention have been shown and described above, the present invention is not limited to the specific embodiments described above, and may be used in the technical field to which the invention pertains without departing from the gist of the invention as claimed in the claims. Of course, various modifications can be made by those skilled in the art, and these modifications should not be understood individually from the technical idea or perspective of the present invention.

1: 3D display system 100: display module
M: Motor 110: Scanning mirror
120: Holographic diffuser 200: Projector module
210: light source 220: fiber combiner
230: collimator 240: TIR prism
250: spatial light modulator 260: projection lens
300: Fixed module 310: Lower frame
320: first fixing part 330: upper frame
340: second fixing part 350: third fixing part

Claims (6)

It is a three-dimensional display system that includes a display module and a projector module.
The display module is,
a scanning mirror that rotates by a motor and reflects light based on a three-dimensional image incident from the projector module; and
A holographic diffuser surrounds the scanning mirror, is provided so that the scanning mirror located inside is rotatable, and provides a three-dimensional image to the viewer by changing the path of light reflected from the scanning mirror,
The projector module is,
A spatial light modulator (SLM) that restores pre-stored holographic data into the three-dimensional image; and
It includes a projection lens that transmits the 3D image restored by the spatial light modulator to the scanning mirror,
The holographic diffuser,
The vertical and horizontal diffusion angles are set differently to form 360-degree multiple viewpoints, providing different images depending on the viewpoint.
The number of viewpoints is determined according to the vertical diffusion angle,
The height of the holographic diffuser is determined according to the minimum viewing distance based on the vertical diffusion angle,
In order to create the view volume, which is the area where the 3D image can be viewed, in the form of a cylinder, the radius of the cylinder is,
Determined by the distance between the projection lens and the center of the view volume and the viewing angle of the projection lens,
A three-dimensional display system, characterized in that the height of the cylinder is determined to be the same as the height of the holographic diffuser. According to paragraph 1,
The holographic diffuser,
By using a holographic optical element (HOE) as a medium, diffraction occurs only at specific wavelengths of light, and wavelengths other than the specific wavelengths pass through, providing a see-through (see-through) image that provides both the three-dimensional image and the external background. A three-dimensional display system characterized by a through type. According to paragraph 2,
The projector module is,
a plurality of light sources that irradiate light containing the specific wavelength;
a fiber combiner combining light emitted from the plurality of light sources;
a collimator that converts the combined light through the fiber combiner into parallel light; and
It includes a TIR (Total Internal Refraction) prism located between the spatial light modulator and the projection lens to cause the parallel light to enter the spatial light modulator and to transmit the three-dimensional image restored from the spatial light modulator to the projection lens. A three-dimensional display system characterized in that. According to paragraph 3,
The projector module is,
A three-dimensional display system characterized in that a three-dimensional image corresponding to the rotation angle of the scanning mirror is transmitted to the scanning mirror based on the rotation speed of the scanning mirror. delete According to paragraph 1,
The holographic diffuser,
A three-dimensional display system provided in a cylindrical shape, wherein the inner diameter is larger than the outer diameter of the scanning mirror.