Holographic display device

Abstract

The invention provides a holographic display device comprising: an illumination unit (100) capable of emitting light to directly illuminate a hologram (104) and form a resulting holographic image (106); wherein the illumination unit (100) comprises an array of individual sub-units (110), each sub-unit (110) comprising a light source and corresponding optics, the illumination unit (100) forming a collimated, diverging or converging light beam as a whole; wherein the array of individual sub-units (110) is arranged at one edge of the hologram (104), wherein the luminance of each sub-unit is adjusted by varying the driving current of each LED of the array respectively to minimize the intensity drop at the edge of the light beam illuminating the hologram compared to the center of the light beam to less than about 5%.

Description

[0001] This application is a divisional application of PCT application filed on September 21, 2018, with international application number PCT / GB2018 / 052703 and invention title "Illumination of Holograms". The date of entry into the Chinese national phase of the PCT application was April 20, 2020, with national application number 201880068245.4 and priority date of September 22, 2017. Technical Field

[0002] This invention relates to an illumination system comprising a compact array of light sources and optics to form a large beam of light to produce collimated, divergent, or convergent beams for illuminating a hologram. Specifically, the invention relates to a first configuration and a second configuration, wherein the first configuration illuminates the hologram from the front with a beam of light, and the second configuration combines the beam with a holographical optical element (HOE) mirror to achieve rear illumination of the reflective hologram. Background Technology

[0003] There is a need in the art for a compact and complete method for uniformly illuminating a displayed hologram that can produce high-quality images. Most commonly, hologram illumination systems employ spotlights placed in front of and above the hologram, which must be positioned at a relatively large distance, comparable to or larger than the size of the hologram itself. This is therefore bulky, unsightly, and impractical in many applications. Furthermore, the illumination from such lights is typically not uniform, being stronger at the center of its distribution. Many applications would benefit from a compact illumination system tightly integrated with the hologram itself. Examples would include displayed holograms to be mounted on a wall, such as ordinary paintings or photographs without obvious additional separate lighting, and automotive brake lights or taillights where there is no space for external lighting.

[0004] Ideally, such a compact lighting system is also insensitive to stray light, especially other typical light sources such as ceiling spotlights or any other light sources used for ambient lighting that emit light close to the direction of the main light source used to illuminate the hologram and result in undesirable secondary images.

[0005] Although previous methods for illuminating holograms exist, all of them have specific difficulties. For example, US 6,366,371 B1, which involves the use of reflective holograms in transmission geometry, has poor efficiency and stray light control.

[0006] The relevant background patents are Dausman's DE 10 2007 022 247 A1 and Ceres' US14 / 253,733, which are incorporated herein by reference.

[0007] Therefore, at least one aspect of the present invention aims to eliminate or mitigate at least one or more of the aforementioned problems.

[0008] Another object of the present invention is to provide an improved apparatus and method for forming a light beam to produce a collimated, divergent, or convergent light beam for illuminating a hologram.

[0009] Another object of at least one aspect of the present invention is to provide an improved holographic display device as a general-purpose graphic medium, suitable for advertising, technical and medical visualization, industrial and consumer applications (e.g., posters, 3D photographs, automotive lighting, etc.). Summary of the Invention

[0010] According to one aspect of the invention, a compact holographic display device is provided, comprising an array of light sources and optics to form a large beam of light, which may be collimated, divergent, or convergent, to illuminate a hologram. Each light source may have corresponding optics configured to nominally collimate the light from that light source.

[0011] A focused beam from an array of sources and optics can be configured to produce a collimated, divergent, or convergent overall beam by adjusting the offset of the individual optics relative to the source.

[0012] According to another aspect of the invention, a beam of light is provided to illuminate the reflective hologram from the same side as the viewer, i.e., the person viewing the hologram.

[0013] According to another aspect of the invention, a combination of a beam of light capable of illuminating the back (i.e., the side opposite the viewer) of a reflective hologram and a holographic optical element (HOE) mirror is provided.

[0014] According to another aspect of the invention, an illumination unit is provided capable of emitting light to illuminate a hologram and form a resulting holographic image, wherein the illumination unit includes an array of individual light sources and corresponding optical devices to form an overall collimated, divergent, or convergent beam of light.

[0015] According to another aspect of the present invention, a holographic display device is provided, the holographic display device comprising: An illumination unit capable of emitting light to illuminate a hologram and form a resulting holographic image, wherein the illumination unit includes an array of individual light sources and optics to form an overall collimated, divergent, or convergent beam of light.

[0016] The holographic display device may also include: At least one mirror that can reflect light from a light source; Among them, the light reflected from the mirror can form a holographic image from the surface of the hologram.

[0017] According to another aspect of the present invention, a holographic display device is provided, comprising: An illumination unit capable of emitting light to illuminate a hologram and form a resulting holographic image, wherein the illumination unit includes an array of various light sources and optical devices to form collimated, divergent, or convergent illumination; At least one mirror that can reflect light from a light source; Holographic surface; Among them, the light reflected from the mirror can form a holographic image from the surface of the hologram.

[0018] Generally speaking, the present invention provides a compact illumination unit that provides a light beam intended for reproducing a holographic image.

[0019] In this invention, an array of smaller light source units replaces the standard point or collimated light source to produce an illumination unit that performs the same function. This array achieves a source brightness similar to that of a standard illumination unit, but with a more compact form.

[0020] It has been found that by providing a more compact illumination unit, the following technical advantages are offered: the array enables the production of low-profile optics, which industrial designers can then use to minimize the size of their holographic illumination systems.

[0021] Therefore, the illumination unit can include an array of small optical units arranged adjacent to one edge of the hologram. The illumination unit can thus form collimated light and a large-area collimated reference beam.

[0022] Therefore, the lighting unit of the present invention can be compact and smaller than the systems used in the prior art. The size of the lighting unit of the present invention can be as follows: Figure 5a and Figure 5b As shown. The dimensions of a conventional light source can be described as DxFL. L The size of the array version according to the invention can be described as DxFL. A In this invention, FL A Compared to FL L Much smaller, and the proportion FL A FL L Less than approximately 0.5:1; Less than approximately 0.25:1; Less than approximately 0.5:1; Less than approximately 0.1:1.

[0023] A compact collimating illumination unit may include multiple light sources or an array of light sources formed by lasers and / or LEDs.

[0024] Holographic display devices may also include a substrate (such as a glass substrate), a hologram attached to the substrate, and an image.

[0025] An array of optical light sources (i.e., optical light units) can be located at any edge of a properly constructed hologram and substrate.

[0026] In a holographic display device, an array facing the light source contains optical elements for forming an illumination beam. These optical elements can be in the form of convex lenses. In alternative embodiments, the elements can be transmissive or reflective curved mirrors or diffractive optics.

[0027] The illumination units can be arranged to form divergent or convergent beams to represent the reference beam used when recording the original hologram.

[0028] Furthermore, the illumination unit can be kept small in size by tightly encapsulating the light unit, which can be achieved by using lens elements formed in, for example, rectangular, hexagonal, or some other suitable mounting shape.

[0029] The holographic display device of the present invention can be used, wherein the light source for reflecting the hologram includes a separate reflective HOE or angle-selective mirror (e.g., WO 2010 / 076571, which is incorporated herein by reference). A substrate (e.g., a glass substrate), a hologram, and a formed illumination image may also be present.

[0030] The present invention also relates to multicolor illumination using collimated arrays. In this embodiment, individual light sources can be used to emit light of different colors, such as emitting different colors of light from different colored LEDs in a single package. Each LED package illuminates a single optics element (lens, mirror, etc.). Because the LEDs are spatially separated, each color exits the optics at a different angle. A dichroic mirror (or HOE mirror) can be used to ensure that multiple wavelengths are collinear by selectively adjusting the angles of reflection of different colors. Thus, an array of light sources can emit colored light that can be controlled and exited to reach the dichroic mirror or HOE. The light can then be reflected to illuminate a hologram, thereby producing a multicolor image.

[0031] The present invention also relates to embodiments in which a display device may include an array of catadioptric collimating elements. The catadioptric elements may include a combination of surfaces for refraction, reflection, and total internal reflection (TIR) ​​of light from a light source. Therefore, the catadioptric elements can use a combination of refractive, reflective, and TIR surfaces to form a light beam. The light beam generated from the array can be used to illuminate a hologram as previously described.

[0032] The present invention also relates to a display device, according to another embodiment of the invention, comprising a collimating element in the form of a parabolic mirror or a universal reflector profile for forming a collimated beam. In these embodiments, a light source (e.g., an LED or laser) may be present to emit light onto the parabolic mirror, which optionally includes a mirror coating. A collimated reference beam that can be used in holographic applications can be formed. An array of parabolic mirrors may be present, wherein each parabolic mirror optionally has a light source (e.g., an LED or laser) located at its focal center. Typically, each parabolic mirror may include a mirror coating and can form a collimated beam that can be used in holographic applications.

[0033] In an alternative embodiment, the display device may include an array of optics for generating a beam of light diverging from a virtual point source. Typically, an array of optics may be present, each optic including an offset light source (e.g., an LED) to generate the beam of light diverging from the virtual point source. The hologram may be illuminated by the display device. In some instances, the reference beam used to illuminate the hologram may not require a collimated beam, but rather a diverging or converging beam. The array of optics of the elements may be configured to generate a beam that appears to diverge from the virtual source point.

[0034] The position of each light source (e.g., an LED) can be off-center relative to its local optical axis. Arrays of refractive optical elements or similar beam shapes can be achieved using other types of optical elements discussed in this application.

[0035] Therefore, the present invention relates to display holograms having a widely acceptable imaging medium suitable for advertising or artistic displays. Alternatively, the resulting holograms can be used for any other commercial purpose for which a fee may be charged.

[0036] The hologram of the present invention can be a transmission hologram or a reflection hologram.

[0037] Generally speaking, the present invention is to provide a display hologram (i.e., a hologram) that can be substantially complete, provide feasible illumination, and optionally be substantially insensitive to stray light.

[0038] The power of the light source can range from approximately 10 W to 500 W in total.

[0039] The light source can be any suitable or appropriate light source, and can be, for example, a laser or an LED or any combination thereof, including multiple of each, for example, red, green and blue lasers or LEDs, or more than three colors.

[0040] In this invention, the light source can be located and / or positioned behind or substantially behind the illuminated reflective hologram (i.e., on the side opposite to the side from which the image is viewed). This contrasts with the general prior art where the light source is positioned in front of the hologram. Therefore, this invention relates to reflective holograms in which one or more light sources are located behind or in front of the formed holographic image.

[0041] One or more light sources can be located and / or positioned within the housing or enclosure. Therefore, one or more light sources can be substantially encapsulated within the holographic display device, thus forming a complete device. This contrasts with prior art systems. In alternative embodiments, one or more light sources can be positioned outside the housing, for example, using a close-up lens.

[0042] Typically, the resulting hologram can be formed on the inner surface / inner side of a housing or enclosure, and then viewed from the outside. Therefore, the display surface can be substantially transparent.

[0043] Holographic display devices may also include optics that can be used to redirect or refocus emitted light onto a desired path for forming a hologram.

[0044] The illumination angle incident on the hologram surface from the illumination array device is relatively high, typically from about 50 to 85 degrees, or preferably from 60 to 85 degrees, and typically at least about 70 degrees.

[0045] According to another aspect of the present invention, a method for forming a holographic image using a holographic display device as described in any of the foregoing aspects is provided.

[0046] According to one aspect of the present invention, a holographic display device is provided, comprising: an illumination unit (100) capable of emitting light to directly illuminate a hologram (104) and form a resulting holographic image (106); wherein the illumination unit (100) comprises an array of respective sub-units (110), each sub-unit (110) comprising a light source and corresponding optics, the illumination unit (100) forming a generally collimated, divergent, or convergent beam of light; wherein the array of the respective sub-units (110) is arranged at one edge of the hologram (104), wherein the brightness of each sub-unit is adjusted by individually changing the driving current of each LED of the array to minimize the intensity drop at the edge of the beam illuminating the hologram compared to the center of the beam to less than about 5%.

[0047] According to one aspect of the present invention, a holographic display device is provided, comprising: an illumination unit (100) capable of emitting light to directly illuminate a hologram (104) and form a resulting holographic image (106); wherein the illumination unit (100) comprises an array of respective sub-units (110), each sub-unit (110) comprising a light source and a corresponding optical device, the illumination unit (100) forming an overall collimated, divergent, or convergent beam of light, wherein the position of each light source is off-center relative to its local optical axis; wherein the array of the respective sub-units (110) is arranged at one edge of the hologram (104), wherein the offset of the light sources within the sub-units is arranged such that the output angle gradually varies between the sub-units.

[0048] According to one aspect of the present invention, a holographic display device is provided, comprising: an illumination unit (100) capable of emitting light to directly illuminate a hologram (104) and form a resulting holographic image (106); wherein the illumination unit (100) comprises an array of sub-units (110), each sub-unit (110) comprising a light source and a corresponding optical element, the illumination unit (100) forming an overall collimated, divergent, or convergent beam of light, wherein each sub-unit is configured to collimate light from a corresponding light source; and wherein the array of the sub-units is arranged such that the illumination unit forms a beam of light having a beam width corresponding to the total width of the array and a collimation corresponding to the collimation achieved by a single light source and a corresponding optical element. Attached Figure Description

[0049] Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which:

[0050] Figure 1a It is a side view representation of a light source and associated optical devices based on existing technology;

[0051] Figure 1b yes Figure 1a The front view shows the light source and associated optical components.

[0052] Figure 2 It is a prior art representation of reflective holograms as described in US 14 / 253,733;

[0053] Figure 3a and Figure 3b The images are side and front views of an array of small optical units arranged at the bottom of a hologram to form a large-area collimating reference beam, according to an embodiment of the present invention.

[0054] Figure 4This is a representation of a collimated light source for reflecting a hologram and including a HOE, according to another embodiment of the present invention;

[0055] Figure 5a and Figure 5b This is a representation of a light source used in a single optical device and collimating illumination array unit according to another embodiment of the present invention;

[0056] Figure 6 This is a representation of multicolor illumination using a collimated array according to another embodiment of the present invention;

[0057] Figure 7a and Figure 7b This is a representation of a low-profile collimated beam using an array of catadioptric elements according to another embodiment of the present invention;

[0058] Figure 8a and Figure 8b This is a representation of a collimating element for forming a collimated beam in the form of a parabolic mirror or universal reflector according to another embodiment of the present invention;

[0059] Figure 9 This is a representation of an array of optical devices for generating a beam of light emanating from a virtual point source, according to another embodiment of the present invention.

[0060] Figure 10a and Figure 10b These are respectively representations of a conventional large lighting system according to the prior art and a compact version utilizing array optics according to another embodiment of the present invention;

[0061] Figure 11a , Figure 11b and Figure 11c An array of optical elements tightly packaged or embedded together according to another embodiment of the invention is shown; and

[0062] Figure 12a and Figure 12b These are representations of intensity uniformity obtained using a conventional large illumination system and intensity uniformity obtained using a compact version of array optics according to another embodiment of the invention. Detailed Implementation

[0063] Generally, embodiments of the present invention involve providing a compact illumination unit that provides a reference beam intended for reproducing a holographic image. An array of smaller light source units replaces the standard light source to perform the same function within a smaller package closely adjacent to the hologram. This array achieves similar light source brightness to a standard illumination unit, but with a more compact form.

[0064] By providing a more compact illumination unit, the following technical advantages are offered: the array enables the production of low-profile optics, which industrial designers can then use to minimize the size of their holographic / illumination systems. The inventors first recognize these technical advantages as discussed and illustrated below.

[0065] Figure 1a This is a side view representation of conventional lighting in the prior art for a reflective hologram 10. It shows a light source 12 (e.g., a laser or LED), a substrate 14 (e.g., a glass substrate), a large illumination unit 16, a mirror or HOE 18, and an image 20.

[0066] Figure 1b yes Figure 1a The front view shown illustrates collimating illumination 22.

[0067] Figure 1a and Figure 1b The disadvantage of the lighting equipment shown is the use of a large lighting unit 16.

[0068] Figure 2 It is a prior art representation of reflective holograms as described in US 14 / 253,733. Figure 2 The image shows a light source 30 (e.g., a laser or LED), a concave mirror or HOE (32), an HOE or angle-selective mirror 34, a hologram 36, and an image 38.

[0069] exist Figure 2 In this configuration, light source 30 is positioned using a typical configuration for transmission holograms. However, a HOE 34 is added for reflective illumination, such that the light now matches the original reference beam of the reflected image hologram. This configuration has several advantages as detailed in patent application US14 / 253,733, which is an application of a prior inventor and is incorporated herein by reference. Such an arrangement has advantages such as being less susceptible to ambient lighting that may reduce the contrast of image 38.

[0070] Figure 1a , Figure 1b and Figure 2 The diagram illustrates the light source and associated optics used to illuminate the hologram and generate an image from it. In both cases, the illumination module extends to at least the full size of the hologram, with the light source and collimating optics positioned at the top and bottom of the hologram, respectively. This has several drawbacks.

[0071] and Figure 1a , Figure 1b and Figure 2Compared to the lighting techniques shown, embodiments of the present invention involve collimated illumination obtained from an array of light sources (i.e., multiple light sources). This provides specific technical advantages, such as a reduction in the size of the lighting unit compared to US 14 / 253,733.

[0072] It has been found that conventional illumination using large-area LED chips and collimators produces an intensity distribution that drops significantly towards the edges of the hologram. This invention addresses this problem. By utilizing a distributed array of smaller light sources, it has been found that a more compact system with more uniform illumination of the hologram can be produced, thus improving the quality of the final holographic image.

[0073] The inventors of this application sought to find an ideal light source for illuminating a holographic image panel, and have discovered that a desirable light source can preferably have at least one or more of the following characteristics: • The wavelength of the light source should match, or match as closely as possible, the wavelength of the holographic recording laser; • The spectral bandwidth of the light source should be smaller than or approximately match the spectral bandwidth of the hologram; and • The light beam from the light source should preferably be configured to match the geometry of the reference beam used to record the hologram and have excellent beam quality (collimation or light concentration) to produce a high-resolution reconstructed holographic image.

[0074] In the following, a compact light source suitable for illuminating holographic panels according to an embodiment of the present invention will be described.

[0075] Figure 3a and Figure 3b This is a representation of an array of small optical sub-units arranged at the bottom of a hologram to form a large-area collimating reference beam, according to an embodiment of the present invention. Each sub-unit includes a light source and collimating optics. Figure 3a This is a side view showing the generation of a collimating light source used for a reflective hologram. Figure 3b This is a front view showing the generation of a collimated light source used for a reflective hologram.

[0076] In particular, Figure 3a An illumination unit 100 in the form of a compact collimating illumination unit is shown. The illumination unit 100 includes an array of light sources, i.e., at least two or more light sources. The size of the compact sub-unit 110 is typically in the range of 5 mm to 50 mm, but is not limited to this range. Typically, a tight package of sub-units in the array is used for maximum optical efficiency.

[0077] The compact collimating illumination unit 100 may include multiple light sources or an array of light sources formed by lasers and / or LEDs. Figure 3aA substrate 102 (e.g., a glass substrate) and an image 106 are also shown, on which the hologram 104 is mounted if it is made of a film. Light from a compact light source 110 is reflected from the substrate 102 to form the hologram 104 and the image 106.

[0078] Figure 3b An array of sub-cells 110 is shown to form collimated illumination for hologram 104. Light from sub-cells 110 is shown emitted as collimated illumination 112.

[0079] therefore, Figure 3a and Figure 3b The present invention is illustrated, and an array of optical units 110 located at the bottom / underside of hologram 104 and substrate 102 is shown. Light is emitted from an array 100 of light sources onto substrate 102 to form hologram 104 and image 106.

[0080] The illumination unit 100 can operate at wavelengths covering the visible spectrum from approximately 400 nm to 640 nm. The subunit 110 has the function of forming a large-area light beam 112.

[0081] By reference Figure 3a And the outline 118 for the compact collimating illumination unit 100, it can be seen that, with Figure 1a and Figure 1b Compared to the dimensions shown in the conventional system, this compact collimating illumination unit has a reduced size.

[0082] Figure 3b An optical element 120 for forming collimated illumination 112 is shown above each of the light sources 110. In this embodiment, the optical element 120 is in the form of a convex lens.

[0083] Each optical subunit 110 is capable of collimating light from a source such as an LED or laser. Collimation can be achieved using a lens, but it can also be achieved using a reflector. The collimation (or beam quality) is equal to or better than that achieved using a lens. Figure 1a and Figure 1b The collimation achieved by a single source / large collimating optics is shown.

[0084] The optical illumination unit 100 forming the light array and the associated sub-units 110 can also be arranged to form an overall diverging or converging beam to represent the reference beam used when recording the original hologram. This can be accomplished by offsetting the light sources within the unit so that the output angle gradually changes between the sub-units.

[0085] The photonic unit 110 can be tightly packaged using lens elements formed in a rectangular, hexagonal, or other suitable mounting shape.

[0086] Figure 4 This is a representation of a collimated light source for reflecting a hologram and including a HOE, according to another embodiment of the present invention. Figure 4 In this configuration, there exists a compact collimating illumination unit 210, which includes, as previously described... Figure 3a and Figure 3b An array of lasers and / or LEDs is described. In this embodiment, a separate reflective HOE or angle-selective mirror 212 is present, as described in US 14 / 253,733. A substrate 214 (e.g., a glass substrate), a hologram 216, and a formed illumination image 218 are also present.

[0087] therefore, Figure 4 The collimated light formed in the process is used with Figure 3a and Figure 3b It is formed by a similar compact collimating illumination unit as described in [the text]. Therefore, it is similar to that formed by [the text] such as [the text] Figure 1a and Figure 1b Compared to the single light source or large collimating optics found in the prior art shown, such a device has the same corresponding technical advantages as previously described, such as reduced size and equivalent collimation (or beam quality).

[0088] Figure 5a and Figure 5b This is a representation of an illumination system based on array optics and individual optics to generate a collimated beam for illuminating a reference beam for a hologram. Specifically, Figure 5a An array (i.e., an N×n sub-unit array) of light sources 310 for forming the collimating illumination unit 312 is shown, such as an array of lasers and / or LEDs. Figure 5a In comparison, Figure 5b There is a single collimator 314 in it.

[0089] exist Figure 5a There are multiple light sources 310 (i.e., an array of light sources 310). Above the light sources 310 there is a series of optical elements 316 for forming collimated light.

[0090] The accompanying diagram helps illustrate how array-based methods can achieve collimated beams with equivalent beam quality to conventional single optical systems. (Refer to...) Figure 5b According to Equation 1, the quality of a collimated beam is defined as the product of the beam width (D) and the sine of the beam divergence angle (q), therefore the beam quality is D × sin(q). (Refer to...) Figure 5aThe beam quality of a single optical sub-unit of the array is d×sin(q), where d is the width of the sub-unit. Since the total width of the array includes the widths of (N) units (d), then (N×d=D), thus producing an array beam quality equivalent to D×sin(q) for a single optics. This is achieved by selecting the size (l) of the LED chip used in the sub-unit optics and the focal length (FL) of the optics. A It has been found that it is possible to match the use of a larger LED chip size (L) and collimator focal length (FL). L The collimation angle (q) is achieved by a conventional illuminator. The equivalence of the collimation angle (q) is ensured by guaranteeing that the ratio of chip size to optical focal length is the same in both cases, i.e., [(l / FL)]. A ) = (L / FL) L To achieve this, use [ ]]. Equation 1

[0091] Therefore, this demonstrates that, as defined by the above-described beam quality definition, an array of light sources proposed in this invention provides a collimated beam equivalent to that of a single optical system.

[0092] The inventors have also discovered that the total luminous flux collected by this array can be ensured to be equal to or higher than the total luminous flux of a conventional single-source option for a large LED chip. Therefore, in conjunction with collimation, the effective brightness of the array can match or exceed the effective brightness of a single LED / optics device. This is achieved through the following... Figure 10a and Figure 10b This will be explained in detail.

[0093] The design of the optical device array in this invention may include the following: A single integrated multi-optical lens / optical device can be replicated using techniques such as injection molding. Stray light between individual optical units is controlled via optical baffles; and Minimize any “grid” pattern in the intensity distribution.

[0094] Ideally, there is no need to actively align the components in the lens array. Therefore, it is possible to place the LED chip on a single PCB and manufacture the lens array with the tolerance to allow the components to snap into place.

[0095] Figure 6 This is a representation of multicolor illumination using a collimated array according to another embodiment of the present invention. Specifically, Figure 6 This diagram illustrates a construction for achieving multi-wavelength illumination using different colored LEDs. A dichroic mirror (or HOE mirror) is used to ensure that the multiple wavelengths are collinear.

[0096] exist Figure 6 In the diagram, there is an array of sub-units 410 in which light is controlled and directed to reach a dichroic mirror or HOE 412. The mirrors 412 are arranged at different angles so that light of different colors becomes collinear. The light is then reflected onto a hologram 416 and then reflected by the hologram 416 to form an image 418.

[0097] Figure 7a and Figure 7b This is a representation of a low-profile collimated beam using an array of catadioptric elements according to another embodiment of the invention. Specifically, Figure 7a A light source 510 in the form of an LED or laser is shown. A mirror coating 512 in the form of a plane mirror is positioned above the light source 510, reflecting light downwards back to a concave surface 514 having a mirror coating 520. Figure 7a As shown, a collimated beam 516 is formed using a combination of refractive and reflective optics. More generally, the combination of refractive and reflective optics is called a catadioptric optics (http: / / www.luxeonstar.com / assets / downloads / carclo-guide.pdf).

[0098] like Figure 7a As shown, total internal reflection (TIR) ​​occurs, for example, at region 518.

[0099] Figure 7b An embodiment is shown in which an array of catadioptric optics 550 for forming a collimated beam 552 is included. As described above, the collimated beam can be used in holographic applications.

[0100] Figure 8a and Figure 8b It is a representation of a collimating element for forming a collimated beam in the form of a parabolic mirror or universal reflector profile according to another embodiment of the invention. Figure 8a The image shows a light source 610 (e.g., an LED or laser) emitting light onto a parabolic mirror 612, which includes a mirror coating 614. (See image.) Figure 8a As shown, this forms a collimated beam 616. As described above, beam 616 can be used in holographic applications.

[0101] Figure 8b An array of parabolic mirrors 650 is shown, each parabolic mirror 650 having a light source 610 (e.g., an LED or laser) located at its focal center. Similar to... Figure 8a Each parabolic mirror 652 includes a mirror coating 654 and forms a collimated beam 656 that can be used in holographic applications.

[0102] Figure 9 This is a representation of an array of optical devices for generating a beam of light emanating from a virtual point source, according to another embodiment of the present invention. Figure 9 The image shows a virtual point source 710. For example... Figure 9 As shown, there is an array of optical devices 712, each optical device including an offset light source 714 (e.g., an LED) to generate a beam of light emanating from a virtual point source 710. A hologram 716 is formed.

[0103] exist Figure 9 In the illustrated embodiments, in some cases, the reference beam used to illuminate the hologram may not require a collimated beam, but rather a diverging or converging beam. The optical array of element 714 can be configured to produce a beam 718 that appears to diverge from the virtual source point 710.

[0104] The position of each light source 714 (e.g., LED) is off-center relative to its local optical axis. Figure 9 The example shown uses an array of refractive optical elements 712; however, similar beam shapes can be achieved using other types of optical elements discussed in this application.

[0105] Figure 10a An example of a conventional collimating illumination unit according to the prior art is shown in detail. Figure 10b An equivalent lighting system based on an array of optical devices with a reduced volume, according to the present invention, is shown in detail.

[0106] exist Figure 10a The image represents conventional illumination with a reflective hologram 810. The left-hand side is a side view of the conventional collimating illumination unit, and the right-hand side is a front view of the conventional collimating illumination unit. A single large-area light source 812 (e.g., a laser or LED), a substrate 814 (e.g., a glass substrate), a large illumination unit 816, a mirror or HOE 818, and an image 820 are shown.

[0107] exist Figure 10b In the diagram, the left side is the side view, and the right side is the front view. (Refer to...) Figure 10b And the outline 918 for the compact collimating illumination unit 900, it can be seen that, with Figure 1a and Figure 1b Compared to the dimensions shown in the conventional system, the compact collimating illumination unit 900 has a reduced size.

[0108] exist Figure 10b On the right-hand side, an optical element 920 for forming collimated illumination 912 is shown above each of the light sources 910. In this embodiment, the optical element 920 is in the form of a convex lens.

[0109] By reference Figure 10b The following details illustrate how an array of optical devices can be more compact and produce a brighter beam compared to a single optical illuminator. The hologram described in detail here measures 200 mm wide by 120 mm high and is illuminated by a reference beam at an angle of incidence of 70 degrees. It should be understood that the volume of any illumination system will be proportional to the area of ​​the hologram being illuminated.

[0110] In this example, based on Figure 10a The dimensions of a standard lighting unit are approximately 200 mm × 120 mm × 40 mm, while Figure 10b The compact array version measures approximately 200 mm × 25 mm × 40 mm, which is almost 1 / 5 the size of a conventional system.

[0111] You can also Figure 10a and Figure 10b The intensity of the two lighting systems shown is compared to illustrate that array-based methods can be designed to produce equal or higher light intensities.

[0112] For comparison, assume both systems have 10 mm. 2 The total LED emitting area is 635 nm; that is, in a conventional system, it has a single 10 mm... 2 The LED chips, and the equivalent array (10 in 2 rows) includes 20 times the 0.5 mm... 2 Smaller area LED chips.

[0113] Therefore, for example, it can be assumed that it comes from Figure 10a and Figure 10b The total LED output flux for each configuration shown is equivalent and equal to approximately 700 lumens. Figure 10a The focal length FL in the conventional system shown L For a single reflector of 120 mm and also through the focal length FL of each individual optical lens element A For approximately 25 mm Figure 10b The array method shown can achieve equivalent collimation with a 1.6-degree extension in the final beam.

[0114] The optical modeling of the two systems shows that in Figure 10a The standard system shown collects approximately 11.4% of the total output LED flux, while for the system according to the invention... Figure 10b The array-based method shown collects approximately 15%. This translates to a final illumination intensity of 35,000 nits for a standard system 10a and for the system according to the invention... Figure 10b The array-based illuminator shown achieves a final illumination intensity of 42,000 nits.

[0115] Figure 11a , Figure 11b and Figure 11c Examples of hexagonal, rhomboid, and square optical elements, respectively, are tightly packaged together according to the present invention. This tight packaging of shapes prevents gaps between the optical elements. If gaps exist, dark bands will appear in the intensity distribution of the illumination beam, which will degrade the quality of the holographic image.

[0116] In particular, Figure 11a A hexagonal optical element 1010 is shown, tightly packaged together without gaps between the different optical elements 1010. An LED chip 1012 is located at the center of the hexagonal optical element 1010.

[0117] Figure 11b A rhomboid optical element 1020 is shown, tightly packaged together without gaps between the different optical elements 1020. An LED chip 1022 is located at the center of the rhomboid optical element 1020.

[0118] Figure 11c A square optical element 1030 is shown, tightly packaged together without gaps between the different optical elements 1030. An LED chip 1032 is located at the center of the square optical element 1030.

[0119] Figure 12a This is an example of intensity uniformity on a reference illumination beam of a single large optical system 1100 according to the prior art. The intensity at the edges of the display can drop to 50% of or less than the intensity at the center of the beam. This is caused by the radiation pattern from the LED and the vignetting of the beam caused by the optics.

[0120] In comparison, Figure 12b The array includes an array of illumination sub-units 1200 according to the invention. The brightness of each illumination sub-unit 1200 can be adjusted, for example, by individually changing the drive current of each LED in the array. In this way, the intensity drop at the edge of the beam compared to the center of the beam can be minimized to less than 5%. The result is an improved holographic image when illuminated with a beam of more uniform intensity. This is a significant improvement over the prior art.

[0121] While specific embodiments of the invention have been described above, it should be understood that deviations from the described embodiments may still fall within the scope of the invention. For example, any suitable type of light source or multiple light sources can be used to form a holographic image. Furthermore, any suitable type of reflective surface (e.g., a mirror) can be used.

[0122] The present invention is also configured as follows. 1. A holographic display device, comprising: An illumination unit capable of emitting light to illuminate a hologram and form a resulting holographic image, wherein the illumination unit comprises an array of sub-units, each sub-unit comprising a light source and corresponding optical devices, and the illumination unit forms an overall collimated, divergent, or convergent beam of light. 2. The holographic display device according to claim 1, wherein the illumination unit comprises an array of smaller illumination sub-units, each smaller illumination sub-unit comprising a light source and corresponding optics to control the overall output beam shape (e.g., collimation), and wherein the smaller sub-units are "tightly packaged" or embedded in the array such that there are no (or negligible) gaps between them. 3. The holographic display device according to claim 2, wherein the array of the smaller illumination sub-units has a periodic structure including square, rectangular or hexagonal structures. 4. The holographic display device according to any of the preceding claims, wherein the illumination unit comprises an array of sub-units arranged at one edge of the hologram. 5. The holographic display device according to any one of the preceding claims, wherein the illumination unit forms a light beam that is used as a light source for reflecting or transmitting a hologram. 6. The holographic display device according to any one of the preceding claims, wherein the illumination unit is compact and includes a plurality of optical elements or an array of optical elements and a plurality of light sources or an array of light sources formed by lasers and / or LEDs. 7. The holographic display device according to any one of the preceding claims, wherein the array of light sources operates at a wavelength of approximately 400 nm to 700 nm. 8. The holographic display device according to any one of the preceding claims, wherein an optical element (e.g., a lens) is positioned near the array of the light source, the optical element (e.g., a lens) being used to form collimated (or divergent or converging) illumination, and wherein the optical element is in the form of a lens or a curved mirror. 9. The holographic display device according to any one of the preceding claims, wherein the collimating illumination unit is used to reflect the hologram and includes a separate reflecting HOE or angle selection mirror such that the reflected hologram is optionally illuminated from the rear, i.e. from the side opposite to the side from which the image is viewed. 10. The holographic display device according to any one of the preceding claims, wherein multicolor illumination is formed, wherein each light source emits light of a different color, such as emitting light of a different color from different colored LEDs; and wherein a dichroic mirror (or HOE mirror) is used to ensure that multiple wavelengths from each illumination subunit are collinear when reflected toward the hologram to form the resulting holographic image. 11. The holographic display device according to any one of the preceding claims, wherein the display device includes a low-profile collimated beam using an array of catadioptric elements, and wherein the catadioptric elements include a convex reflective surface and a mirror positioned above the convex reflective surface to reflect light downward back to the convex reflective surface, and wherein the catadioptric elements use a combination of refractive and reflective optics to form the collimated beam. 12. The holographic display device according to any one of the preceding claims, wherein the display device includes an array of parabolic mirrors or a universal reflector profile to form a collimated beam. 13. The holographic display device according to any one of the preceding claims, wherein the display device includes an array of optical devices for generating a total beam of light emanating from a virtual point source. 14. The holographic display device according to any one of the preceding claims, wherein there is an array of optical elements, each of the optical elements in the array including an offset light source (e.g., an LED) for generating a total beam of light emanating from a virtual point source. 15. The holographic display device according to 14, wherein the position of each light source (e.g., an LED) is off-center relative to its local optical axis in order to generate a uniform light beam that propagates at an angle to the illumination unit.

Claims

1. A holographic display device, comprising: An illumination unit (100) is capable of emitting light to directly illuminate the hologram (104) and form a resulting holographic image (106). The lighting unit (100) includes an array of sub-units (110), each sub-unit (110) including a light source and corresponding optical devices, and the lighting unit (100) forms an overall collimated, divergent or convergent beam of light. The array of the various sub-units (110) is arranged at one edge of the hologram (104), wherein the brightness of each sub-unit is adjusted by individually changing the driving current of each light source of the array to minimize the intensity drop at the edge of the beam illuminating the hologram compared to the center of the beam to less than about 5%.

2. The holographic display device according to claim 1, wherein, The array of the sub-units (110) is "tightly encapsulated" or embedded in the array.

3. The holographic display device according to claim 1 or claim 2, wherein, The array of sub-units (110) has a square, rectangular or hexagonal shape.

4. The holographic display device according to claim 1, wherein, The array of each subunit (110) includes a light source formed by a laser and / or an LED and an array of corresponding optical elements.

5. The holographic display device according to claim 3, wherein, The light source operates at a wavelength of approximately 400 nm to 700 nm.

6. The holographic display device according to claim 1, wherein, The display device includes a collimated beam using an array of catadioptric elements (550), wherein the catadioptric elements (550) include a convex reflective surface and a refractive surface, wherein a mirror is positioned above the convex reflective surface to reflect light downward back to the convex reflective surface, and wherein the catadioptric elements (550) use a combination of refractive and reflective optics to form the collimated beam.

7. The holographic display device according to claim 1, wherein, The display device includes a collimating element in the form of a general reflector profile.

8. The holographic display device according to claim 1, wherein, The display device generates a total beam of light emanating from the virtual point source (710).

9. A holographic display device, comprising: An illumination unit (100) is capable of emitting light to directly illuminate the hologram (104) and form a resulting holographic image (106). The illumination unit (100) includes an array of sub-units (110), each sub-unit (110) including a light source and corresponding optical devices. The illumination unit (100) forms an overall collimated, divergent, or convergent beam of light, wherein the position of each light source is off-center relative to its local optical axis. The array of each sub-unit (110) is arranged at one edge of the hologram (104), and the offset of the light source within the sub-unit is arranged such that the output angle gradually changes between the sub-units.

10. The holographic display device according to claim 9, wherein, The illumination unit (100) forms a beam of light that is used as a light source for reflecting or transmitting holograms.

11. The holographic display device according to claim 9, wherein, The array of each subunit (110) includes a light source formed by a laser and / or an LED and an array of corresponding optical elements.

12. The holographic display device according to claim 11, wherein, The optical elements are positioned in an array close to the light source, the optical elements are used to form collimated illumination, and the optical elements are in the form of lenses or curved mirrors.

13. The holographic display device according to claim 9, wherein, The display device includes a collimated beam using an array of catadioptric elements (550), wherein the catadioptric elements (550) include a convex reflective surface and a refractive surface, wherein a mirror is positioned above the convex reflective surface to reflect light downward back to the convex reflective surface, and wherein the catadioptric elements (550) use a combination of refractive and reflective optics to form the collimated beam.

14. The holographic display device according to claim 9, wherein, The display device includes a collimating element in the form of a general reflector profile.

15. A holographic display device, comprising: An illumination unit (100) is capable of emitting light to directly illuminate the hologram (104) and form a resulting holographic image (106). The illumination unit (100) includes an array of sub-units (110), each sub-unit (110) including a light source and corresponding optical devices, the illumination unit (100) forming an overall collimated, divergent or convergent beam of light, wherein each sub-unit is configured to collimate light from a corresponding light source; Furthermore, the array of sub-units is arranged such that the illumination unit forms a beam having a beam width corresponding to the total width of the array and a collimation corresponding to the collimation achieved by a single light source and corresponding optical element.

16. The holographic display device according to claim 15, wherein, The array of each subunit (110) includes a light source formed by a laser and / or an LED and an array of corresponding optical elements.

17. The holographic display device according to claim 15, wherein, The display device includes a collimated beam using an array of catadioptric elements (550), wherein the catadioptric elements (550) include a convex reflective surface and a refractive surface, wherein a mirror is positioned above the convex reflective surface to reflect light downward back to the convex reflective surface, and wherein the catadioptric elements (550) use a combination of refractive and reflective optics to form the collimated beam.

18. The holographic display device according to claim 15, wherein, The display device includes a collimating element in the form of a general reflector profile.

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