RU2572286C1 - Rear illumination device and hologram writing circuit - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: rear illumination plate comprises light source, optical element, wave guide plate with the front, rear, top and bottom surfaces. The first holographic element is arranged at the rear side of said plate while second holographic element is arranged at the bottom side of said plate. Optical element allows the uniform illumination of the first holographic element via wave guide plate by the light beam from the light source. Wave guide plate allows the propagation of light beam incident on the plate front surface toward the first holographic element without the full internal reflection. The first holographic can collimate and redirect the light beam to the second holographic element. Note here that the second holographic element can output the collimated light beam from wave guide plate through the top surface.

EFFECT: decreased non-uniformity of brightness and depth of the rear illumination device.

29 cl, 8 dwg

Description

FIELD OF THE INVENTION

The present invention relates generally to optical technology and, in particular, to backlight devices using a combination of a light guide plate and holographic elements, and a hologram recording circuit used to record said holographic elements. The proposed backlight devices are particularly applicable for backlighting in mobile devices, such as mobile phones, and imaging systems, such as 3D or holographic displays.

BACKGROUND

An important characteristic of modern backlight systems (backlight modules, BLU) is their thickness, which must be minimized. For this purpose, two approaches to the design of BLU are used: direct backlight and end backlight. In the case of end backlighting, light sources are located at the ends of the light guide plate, as a rule, perpendicular to the illumination region. End backlighting is the most promising way to design BLUs with minimal thickness.

As a rule, laser diodes are used as light sources for end backlighting. Laser diodes are located at the ends of the light guide plate and have a limited width (usually 5-6 mm). In known solutions, the thickness of the BLU depends mainly on the laser diode, and not on the thickness of the light guide plate.

The challenge is to ensure high uniformity and high collimation of light for illumination and to reduce losses associated with scattering in the waveguide.

No. 5,465,311 describes a device 700 for reconstructing holographic images using a waveguide 702 and conventional light sources (see FIG. 7). The waveguide 702 receives light through the communication element 704 and ensures the propagation of the received light within itself due to total internal reflection. The holographic element 706, made on a holographic emulsion, is designed to output incident light from the waveguide 702. The output light is used to reconstruct holographic images from a holographic emulsion located on the surface of the waveguide. This waveguide structure is configured to provide highly efficient reconstruction of holograms, while using conventional light sources, and allows the use of beam diameters greater than the thickness of the waveguide. This solution is the simplest and most effective for lighting a traditional LCD display using an incoherent light source or lighting a holographic display with a coherent light source. However, this solution has a gradient decrease in brightness (inhomogeneity of lighting).

US 5,854,697 describes a backlight device 800 using a holographic element or spatial light modulator (SLM) based on a waveguide and a coherent light source (see FIG. 8). The device 800 comprises a thin substrate waveguide 802, on the surface of which there is a holographic element 804. The light source is optically coupled to the waveguide 802 so that the light emitted by the source is forced to propagate along the waveguide 802, while leaving the waveguide 802 at points of contact with the surface waveguide 802 on which a holographic element 804 is formed. Radiation output portionwise by the holographic element 804 can advantageously be used to illuminate holographic elements or ostranstvennyh light modulators. This waveguide structure provides uniform emission of the amount of light by means of a holographic element 804 along the length of the holographic element 804. This solution is the simplest and most effective coherent light source for illuminating a holographic display. In this case, a high uniformity of lighting is achieved. However, this solution leads to a superposition of a plurality of repeatedly reflected coherent beams, as a result of which interference fringes are formed. Device 800 generates only one observation area when using SLM (no surround effect). In addition, this solution does not have an effective means for uniformly introducing light into a wide or thin waveguide.

Thus, the known solutions used for holographic displays have a non-uniform and diffusely scattered output illumination, thereby not providing a volumetric effect (i.e. they form only one observation zone).

SUMMARY OF THE INVENTION

An object of the present invention is to overcome the aforementioned disadvantages inherent in solutions known in the art.

According to a first aspect, a backlight device is provided. The device comprises at least one light source, at least one optical element, a light guide plate and the first and second holographic elements. The light guide plate has a front surface, a rear surface, an upper surface and a lower surface. The first holographic element is located on the rear surface of the light guide plate, and the second holographic element is located on the lower surface of the light guide plate. The optical element is configured to provide uniform illumination of the first holographic element through the light guide plate with a beam of light from a light source. The light guide plate is configured to propagate a beam of light incident on the front surface of the light guide plate in the direction of the first holographic element without total internal reflection. The first holographic element is configured to collimate and redirect the light beam to the second holographic element. The second holographic element is configured to output a collimated light beam from the light guide plate through the upper surface of the light guide plate.

In one embodiment, the light source is one of the following: an LED, a laser diode, a solid state laser, or a fiber laser.

In one other embodiment, the optical element is one of the following: a concave lick, a convex lens, a transmissive holographic element, or a reflecting holographic element.

The light guide plate may be made of one of the following: high transmittance plastics, optical glasses or silica glass.

In yet another embodiment, the second holographic element is made in the form of a field lens forming at least two focused observation zones at a fixed distance from the light guide plate.

The light guide plate may have a constant cross section along its length, and in particular, this cross section may be rectangular.

The first and second holographic elements can be made in the form of gratings. The first and second holographic elements can be made of optically transparent materials.

Each of the front, rear, upper and lower surfaces of the light guide plate may be flat.

The proposed backlight device can be adapted for backlighting in mobile devices, such as mobile phones, and visualization systems, such as 3D or holographic displays.

According to a second aspect, a backlight device is provided. The device comprises at least one light source, at least one optical element, a light guide plate and the first and second holographic elements. The light guide plate has a front surface, a rear surface, an upper surface and a lower surface. The first holographic element is located on the rear surface of the light guide plate, and the second holographic element is located on the upper surface of the light guide plate. The optical element is configured to provide uniform illumination of the first holographic element through the light guide plate with a beam of light from a light source. The light guide plate is configured to propagate a beam of light incident on the front surface of the light guide plate in the direction of the first holographic element without total internal reflection. The first holographic element is configured to collimate and redirect the light beam to the second holographic element. The second holographic element is made in the form of a transmitting holographic element for outputting a collimated beam of light from the light guide plate through the upper surface.

The backlight device according to the second aspect has embodiments similar to the embodiments mentioned above with respect to the backlight device according to the first aspect.

According to a third aspect, a hologram recording scheme is proposed. The circuit is used to separately record the first and second holographic elements of the backlight devices according to the first and second aspects. The circuit includes: a light source configured to emit light radiation, a divider configured to divide the emitted light radiation into a reference beam and a signal beam, a reference path for propagating the reference beam, a signal path for propagating the signal beam, a light guide plate located between outputs of the reference and signal paths, a holographic element located on one of the surfaces of the light guide plate, and a photosensitive medium, Assumption in optical contact with said one surface of the light guide plate. The reference path is configured to allow the reference beam to propagate through the light guide plate and the holographic element to the photosensitive medium on the one hand, and the signal path is configured to allow the signal beam to propagate to the photosensitive medium on the other hand.

As noted above, the light source may be one of the following: an LED, a laser diode, a solid state laser, or a fiber laser.

In one embodiment, the circuit further comprises a half-wave plate located between the light source and the divider and configured to adjust the polarization state of the emitted light radiation.

If necessary, each of the reference and signal paths may contain one or more means of filtering, collimating, and redirecting the corresponding of the reference and signal beams.

In one embodiment, the circuit further comprises a field lens at the output of the signal path.

In one embodiment, the circuit further comprises a coverslip located in optical contact with the photosensitive medium from the other side, to reduce noise due to repeated reflections in the signal path.

In one embodiment, the circuit further comprises a shutter located at the output of the light source and configured to control the exposure time for the light source.

Using a combination of the above light guide plate and two holographic elements, the present invention provides multi-color coherent illumination suitable for backlighting in 3D or holographic displays.

In addition, the combination of the aforementioned light guide plate and two holographic elements provides illumination of 3D or holographic displays with achromatic coherent light, while reducing the heterogeneity of brightness and thickness of the backlight device.

Other features and advantages of the present invention will become apparent after reading the following detailed description and viewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The essence of the present invention is illustrated by the accompanying drawings, in which:

FIG. 1 shows one example of a backlight device outputting collimated beams of light;

FIG. 2 shows one example of a backlight device forming focused observation zones;

FIG. 3 shows one example of a hologram recording circuit for recording a second holographic element of FIG. 1-2;

FIG. 4 shows one example of a hologram recording circuit for recording the second holographic element of FIG. 1-2;

FIG. 5 shows one example of a hologram recording circuit for recording the first holographic element of FIG. 1-2;

FIG. 6 shows an auxiliary view of the hologram recording circuit of FIG. 5;

FIG. 7 shows one solution known in the art;

FIG. 8 shows one other solution known in the art.

DETAILED DESCRIPTION OF THE INVENTION

Various embodiments of the present invention are described in more detail below with reference to the accompanying drawings. However, the present invention can be implemented in many other forms and should not be construed as being limited by any particular structure or function as described in the following description. In contrast, these embodiments are provided in order to make the description of the present invention detailed and complete. Based on the present description, it will be obvious to a person skilled in the art that the scope of the present invention covers any embodiment of the present invention that is disclosed herein, regardless of whether this embodiment is implemented independently or in conjunction with any other embodiment of the present invention . For example, the device disclosed herein may be practiced by using any number of embodiments provided herein. In addition, it should be understood that any embodiment of the present invention can be implemented using one or more of the elements presented in the attached claims.

The word “exemplary” is used herein to mean “used as an example or illustration”. Any embodiment described herein as “exemplary” need not be construed as preferred or having an advantage over other embodiments.

In addition, terminology associated with the direction, such as “upper”, “lower”, “front”, “back”, etc., is used with reference to the orientation of the described figures. Since the components of the embodiments of the present invention can be arranged in different orientations, terminology associated with the direction is used for purposes of illustration and not limitation. It should be understood that other embodiments may be used and structural or logical substitutions may be made without departing from the scope of the present invention.

FIG. 1 illustrates a backlight device 100 in accordance with one exemplary embodiment of the present invention. As shown, the backlight device 100 comprises two light sources 102, two optical elements 104, a light guide plate 106, a first holographic element 108 and a second holographic element 110. The light guide plate 106 has a front surface 112, a rear surface 114, an upper surface 116 and a lower surface 118. The first holographic element 108 is located on the rear surface 114 of the light guide plate 106, and the second holographic element 110 is located on the lower surface 118 of the light guide plate 106.

The light sources 102 are configured to emit light beams in the direction of the optical elements 104. Each of the light sources 102 may comprise a laser diode, an LED, a solid state laser, or a fiber laser. However, the present invention is not limited to such types of light sources, and any other suitable light sources may be used, as should be apparent to those skilled in the art.

Optical elements 104 are configured to provide uniform illumination of the first holographic element 108 by light beams from light sources 102. Each of the optical elements 104 may comprise a concave lens, a convex lens, a transmission holographic element, a reflecting holographic element, or any combination thereof.

Although FIG. 1 illustrates two identical light sources 102 and two identical optical elements 104, it will be apparent to those skilled in the art that any number and any types of said components may be used, depending on the particular application.

The light guide plate 106 is configured to allow light beams to propagate from the light sources 102 in the direction of the first holographic element 108 without the effect of total internal reflection inside the light guide plate 106. In other words, the light beams are not reflected from the front (112), upper (116) and lower ( 118) the surfaces of the light guide plate 106 as they propagate within the light guide plate 106. The light guide plate 106 may have any specific shape suitable for such light propagation. As an example, FIG. 1 illustrates a light guide plate 106 having a rectangular cross section. Furthermore, the cross section of the light guide plate 106 is constant along the length of the light guide plate 106. However, the present invention is not limited to this configuration of the light guide plate 106. Suitable materials of the light guide plate 106 include high transmittance plastic, optical glasses, silica glass.

The first holographic element 108 is used as a collimating and redirecting holographic element. In particular, the first holographic element 108 is configured to collimate the light beams from the light sources 102 and redirect the collimated light beams to a second holographic element 110 located on the lower surface 118 of the light guide plate 106. The second holographic element 110 is used as the output holographic element for outputting light beams from the light guide plate 106 through the upper surface 116. The first and second holographic elements 108 and 110 can be made in the form of brushes with suitable periods and / or suitable selectivity for wavelength and / or angle, as should be apparent to those skilled in the art.

The second holographic element 110 can be made in the following two ways. According to the first embodiment, the second holographic element 110 is configured to provide at least two collimated output beams, as shown in FIG. 1. In the second embodiment, the second holographic element 110 functions as a field lens and forms at least two focused observation zones at a fixed distance from the light guide plate 106 (see Fig. 2). Thus, the output beams of light illuminate a holographic display (not shown) by a plane wavefront or a converging wavefront, depending on these options of the second holographic element 110.

The proposed backlight device 100 may provide at least two so-called optical channels (according to the number of light sources 102). In particular, the device 100 forms the left (120) and right (122) surveillance zones (see Figs. 1-2). Each of these zones is formed by a single light source 102, one optical element 104 and shared light guide plate 106, the first and second holographic elements 108, 110. The angle 2φ between the two optical channels is determined by the observation distance and the stereoscopic basis.

FIG. 3 shows a schematic representation of a hologram recording circuit 300 used to record the second holographic element 110. The radiation from the laser 302 is divided by a polarizing beam splitter 304 into the reference and signal beams passing through the reference path 306 and the signal path 308, respectively. The polarization state of the beams is adjusted by a half-wave plate 310. In each of the paths 306 and 308, the beams are filtered by means of microholes (pin-halls) 312, collimated by lenses 314, cut off by rectangular apertures and sent to the photosensitive medium 316 from opposite sides. The photosensitive medium 316 is in optical contact with the bottom surface 118 of the light guide plate 106. The reference beam is passed through the light guide plate 106. To reduce noise due to repeated reflections in the signal path 308, the cover glass 318 is in optical contact with the photosensitive medium 316. The shutter 320 controls the exposure time . The circuit 300 also contains various mirrors M1-M3, apertures D1-D2, and micro lenses O1-O2, which are used to ensure proper light distribution, as should be apparent to those skilled in the art.

FIG. 4 shows a schematic representation of a hologram recording circuit 400 used to record a second holographic element 110 in the case where two focused viewing zones 120 and 122 are formed at a fixed distance, as shown in FIG. 2. The circuit 400 contains all the components of the system 300 and additionally a field lens 322 located in the signal path 308.

FIG. 5 shows a schematic representation of a hologram recording circuit 500 used to record the first holographic element 108. The radiation from the laser 502 is divided by a polarizing beam splitter 504 into the reference and signal beams passing through the reference path 506 and the signal path 508, respectively. The polarization state of the beams is adjusted by half-wave plates 510. In paths 506 and 508, the beams are filtered by microholes (pin-halls) 512, collimated by lenses 514, cut off by a rectangular aperture 516 in the reference path 506 and by a slit 518 in the signal path 508 and sent to a photosensitive medium (not shown) from opposite sides. The photosensitive medium is in optical contact with the rear surface 114 of the light guide plate 106. The reference beam is passed through the light guide plate 106. The required divergence of the reference beam is achieved by using a cylindrical concave lens 520. The shutter 522 controls the exposure time. The circuit 500 also contains various mirrors M1-M3, apertures D1-D2, and micro lenses O1-O2, which are used to ensure proper light distribution, as should be apparent to those skilled in the art. FIG. 6 is an auxiliary view (“View A” in FIG. 5) for clarity.

The first holographic element 108 located on the rear surface 114 of the light guide plate 106 and the second holographic element 110 located on the lower surface 118 of the light guide plate 106 should be recorded independently of each other. This allows you to adjust the output parameters of the entire system by controlling the parameters of each of these holographic elements.

Example

Below are shown the preferred parameters of the proposed backlight device:

- lighting area: 86 × 35 mm ² (diagonal size: 3.6 ”);

- thickness of the backlight device: 10 mm;

- uniformity of lighting: 90% (measured in accordance with VESA FLAT PANEL DISPLAY MEASUREMENTS STANDARD Version 2.0);

- for a backlight device with collimated output radiation, collimation angle: ± 0.038 °;

- for a backlight device with a fixed field lens, the field of view is provided at a distance of 600 mm with a stereoscopic basis of 62 mm;

- angle 2φ between two optical channels: ± 3 °.

Although exemplary embodiments of the present invention have been disclosed herein, it should be noted that in these embodiments of the present invention, any changes and modifications can be made without departing from the scope of legal protection that is determined by the attached claims. In the appended claims, reference to the singular does not exclude the presence of a plurality of such elements unless explicitly stated otherwise.

Claims (29)

1. The backlight device containing:
at least one light source;
at least one optical element;
a light guide plate having a front surface, a rear surface, an upper surface and a lower surface;
a first holographic element located on the rear surface of the light guide plate; and
a second holographic element located on the lower surface of the light guide plate;
wherein the optical element is configured to provide uniform illumination of the first holographic element through the light guide plate with a beam of light from a light source;
the light guide plate is configured to propagate a beam of light incident on the front surface of the light guide plate in the direction of the first holographic element without total internal reflection;
the first holographic element is configured to collimate and redirect the light beam to the second holographic element; and
the second holographic element is configured to output a collimated light beam from the light guide plate through the upper surface. 2. The backlight device according to claim 1, wherein the light source is one of the following: an LED, a laser diode, a solid state laser, or a fiber laser. 3. The backlight device according to claim 1, wherein the optical element is one of the following: a concave lens, a convex lens, a transmission holographic element or a reflecting holographic element. 4. The backlight device according to claim 1, wherein the light guide plate is made of one of the following: high transmittance plastics, optical glasses or quartz glass. 5. The backlight device according to claim 1, in which the second holographic element is made in the form of a field lens forming at least two focused observation zones at a fixed distance. 6. The backlight device according to claim 1, wherein the light guide plate has a constant cross section along its length. 7. The backlight device according to claim 6, in which the cross section of the light guide plate is rectangular. 8. The backlight device according to claim 1, in which the first and second holographic elements are made in the form of gratings. 9. The backlight device according to claim 1, wherein the first and second holographic elements are made of optically transparent materials. 10. The backlight device according to claim 1, in which each of the front, rear, upper and lower surfaces of the light guide plate is flat. 11. The backlight device according to claim 1, made with the possibility of use in a mobile device or visualization system. 12. A backlight device comprising:
at least one light source;
at least one optical element;
a light guide plate having a front surface, a rear surface, an upper surface and a lower surface;
a first holographic element located on the rear surface of the light guide plate; and
a second holographic element located on the upper surface of the light guide plate;
wherein the optical element is configured to provide uniform illumination of the first holographic element through the light guide plate with a beam of light from a light source;
the light guide plate is configured to propagate a beam of light incident on the front surface of the light guide plate in the direction of the first holographic element without total internal reflection;
the first holographic element is configured to collimate and redirect the light beam to the second holographic element; and
the second holographic element is made in the form of a transmitting holographic element for outputting a collimated beam of light from the light guide plate through the upper surface. 13. The backlight device according to claim 12, wherein the light source is one of the following: an LED, a laser diode, a solid state laser, or a fiber laser. 14. The backlight device according to claim 12, in which the optical element is one of the following: a concave lens, a convex lens, a transmission holographic element or a reflecting holographic element. 15. The backlight device according to claim 12, in which the light guide plate is made of one of the following: high transmittance plastics, optical glasses or quartz glass. 16. The backlight device according to claim 12, in which the second holographic element is made in the form of a field lens forming at least two focused observation zones at a fixed distance. 17. The backlight device according to claim 12, in which the light guide plate has a constant cross section along its length. 18. The backlight device according to claim 17, in which the cross section of the light guide plate is rectangular. 19. The backlight device according to claim 12, in which the first and second holographic elements are made in the form of gratings. 20. The backlight device according to claim 12, in which the first and second holographic elements are made of optically transparent materials. 21. The backlight device according to claim 12, in which each of the front, rear, upper and lower surfaces of the light guide plate is flat. 22. The backlight device according to p. 12, made with the possibility of use in a mobile device or visualization system. 23. A hologram recording scheme comprising:
a light source configured to emit light radiation;
a divider configured to divide the emitted light radiation into a reference beam and a signal beam;
reference path, providing the distribution of the reference beam;
signal path, providing propagation of the signal beam;
a light guide plate located between the outputs of the reference and signal paths;
a holographic element located on one of the surfaces of the light guide plate;
a photosensitive medium located in optical contact with said one of the surfaces of the light guide plate;
wherein the reference path is configured to allow the reference beam to propagate through the light guide plate and the holographic element to the photosensitive medium on the one hand, and the signal path is configured to allow the signal beam to propagate to the photosensitive medium on the other hand. 24. The circuit of claim 23, wherein the light source is one of the following: an LED, a laser diode, a solid state laser, or a fiber laser. 25. The circuit of claim 23, further comprising a half-wave plate located between the light source and the divider and configured to adjust the polarization state of the emitted light radiation. 26. The circuit of claim 23, wherein each of the reference and signal paths comprises one or more means of filtering, collimating, and redirecting the corresponding of the reference and signal beams. 27. The circuit of claim 26, further comprising a field lens at the output of the signal path. 28. The circuit of claim 23, further comprising a coverslip located in optical contact with the photosensitive medium from said other side to reduce noise due to repeated reflections in the signal path. 29. The circuit of claim 23, further comprising a shutter located at the output of the light source and configured to control exposure time for the light source.

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