CN114859680A - Hologram generation method, control unit, projection device and head-up display - Google Patents
Hologram generation method, control unit, projection device and head-up display Download PDFInfo
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Abstract
The invention provides a hologram generation method, a control unit, a projection device and a head-up display, wherein the method respectively obtains first complex amplitudes corresponding to all display depths according to the focal length of a first lens group and n display depths; calculating a first phase of a plane where the spatial light modulator is located according to a first complex amplitude corresponding to the kth display depth, image information on the plane where the kth display depth is located and an initial phase, and updating the initial phase to the first phase; and repeatedly executing the steps to finish an iterative process of calculating the first phase from the 1 st display depth to the nth display depth, and when the iterative process is finished for a preset number of times, taking the finally obtained first phase as the pure phase hologram to be loaded into the spatial light modulator. By generating the hologram through the method, the projection device can form images on multiple depths, 3D display is realized, and the depth range of the 3D display is improved.
Description
Technical Field
The embodiment of the invention relates to the technical field of optics, in particular to a hologram generation method, a control unit, a projection device and a head-up display.
Background
Augmented Reality Head-Up Display (AR-HUD) is the most critical Display system in the intelligent cockpit of new generation, can fuse virtual image and real driving scene, provides panel board information, road guide information etc. for the driver, avoids the driver to drive in-process and lowers the Head and watch the panel board, reduces driving risk, promotes and drives experience.
At present, an AR-HUD system mostly adopts a projection system based on a combination of free-form surface mirrors, and displays an image through a Thin film transistor liquid crystal display (TFT-LCD) or a Digital Micromirror Device (DMD), however, this method can only realize two-Dimensional display, and the displayed image is fused with a real driving scene through perspective transformation projection, and due to lack of real Three-Dimensional (3D) information, the fusion accuracy is poor, and an error is easily generated in the judgment of a driver on the depth, so that the requirement for realizing the 3DAR-HUD gradually changes.
Realizing 3D shows often in AR-HUD following mode, the first is through providing the two-dimensional image that contains the parallax image to user left and right eyes respectively, utilize binocular parallax, after user left and right eyes observed the two-dimensional image respectively, the brain can synthetic image form 3D perception, nevertheless because the two-dimensional display surface depth is fixed and experience the image depth change, people's eye focus and regulation produce the contradiction, lead to the giddiness easily, when realizing 3D and showing closely, watch travelling comfort and cognitive accuracy are relatively poor, be unfavorable for practical application. Other methods such as the integrated imaging 3D display based on the microlens array or the light field 3D display based on the multi-depth superposition are adopted, but these methods can only reduce the influence of the convergence adjustment conflict to some extent, and the depth range of the 3D display is limited to some extent.
Disclosure of Invention
The embodiment of the invention provides a hologram generation method, a control unit, a projection device and a head-up display, wherein the hologram is generated by the hologram generation method, so that the projection device can form images on multiple depths, 3D display is realized, and the 3D display depth range is improved.
One technical solution adopted in an embodiment of the present invention is to provide a hologram generating method, which is applied to a projection device, the projection device includes a spatial light modulator and a first lens group, the spatial light modulator is disposed on a front focal plane of the first lens group, the spatial light modulator is configured to load a hologram and modulate received illumination light according to the hologram to generate a three-dimensional image light field, and the first lens group is configured to display the three-dimensional image information light field to form a three-dimensional image, where the method includes: step S100: acquiring an initial phase of a plane where the spatial light modulator is located, a focal length of the first lens group, n display depths of the three-dimensional image and image information of the three-dimensional image on the plane where the n display depths are located, wherein n is not less than 2 and is an integer; step S200: respectively obtaining a first complex amplitude corresponding to each display depth according to the focal length and the n display depths; step S300: calculating a first phase of a plane where the spatial light modulator is located according to the first complex amplitude corresponding to the kth display depth, the image information on the plane where the kth display depth is located and an initial phase, and updating the initial phase to the first phase, wherein k is greater than or equal to 1 and less than or equal to n, and is an integer; step S400: repeatedly executing the step S300 to finish one iteration process of calculating the first phase from the 1 st display depth to the nth display depth; step S500: and continuing to repeatedly execute the step S300 until the iteration process is completed for a preset number of times, and taking the finally obtained first phase as a pure phase hologram to be loaded by the spatial light modulator.
In some embodiments, the initial phase of the plane of the spatial light modulator comprises a random phase or a quadratic phase.
In some embodiments, the step S300 includes: step S310: obtaining a second complex amplitude of the plane where the spatial light modulator is located according to the initial phase and the first complex amplitude corresponding to the kth display depth; step S320: performing two-dimensional Fourier transform on the second complex amplitude to obtain a frequency spectrum corresponding to the second complex amplitude; step S330: carrying out weight superposition on the image information on the plane where the kth display depth is located and the amplitude of the frequency spectrum, and reserving the phase of the frequency spectrum to obtain the frequency spectrum after weight; step S340: performing two-dimensional inverse Fourier transform on the weighted frequency spectrum to obtain a third complex amplitude on the plane where the spatial modulator is located; step S350: and obtaining the first phase according to the third complex amplitude and the first complex amplitude corresponding to the kth display depth, and updating the initial phase to the first phase.
In some embodiments, the step S310 includes: step S311: obtaining a fourth complex amplitude of the plane where the spatial light modulator is located according to the initial phase; step S312: and obtaining the second complex amplitude according to the conjugate of the first complex amplitude corresponding to the kth display depth and the fourth complex amplitude.
In some embodiments, the step S330 includes: obtaining the weighted spectrum F by the following formula zk ′：
wherein ,
A zk ＝|F zk |/max{|F zk |}；P k on the plane of the kth display depthThe image information epsilon is a weight factor corresponding to the image information on the plane where the kth display depth is located, | F zk | is the frequency spectrum F zk Modulo of (max { | F) zk Denotes a pair | F zk L maximum, angle { F |) zk Denotes a pair F zk And taking the phase.
In some embodiments, the first complex amplitude for the kth display depth is
wherein ,
z k is the k display depth of the three-dimensional image, lambda is the wavelength, f 1 Is the focal length of the first lens group, (x, y) is the coordinate on the plane where the spatial light modulator is located.
In a second aspect, an embodiment of the present invention further provides a control unit, including: at least one processor; and a memory communicatively coupled to the at least one processor; wherein the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the hologram generation method according to any one of the first aspect.
In a third aspect, an embodiment of the present invention provides a projection apparatus, including: an illumination unit, a spatial light modulator, a first lens group, a second lens group, a two-dimensional scanning galvanometer, and a control unit as described in the second aspect; the spatial light modulator is arranged in the light emergent direction of the illuminating unit, the first lens group, the second lens group and the two-dimensional scanning galvanometer are sequentially arranged in the light emergent direction of the spatial light modulator, the spatial light modulator is arranged on a front focal plane of the first lens group, and the control unit is respectively connected with the spatial light modulator and the two-dimensional scanning galvanometer; wherein the illumination unit is used for generating illumination light; the spatial light modulator is used for loading the pure phase hologram and modulating the received illumination light according to the pure phase hologram so as to generate a three-dimensional image light field; the first lens group is used for displaying the three-dimensional image light field once; the second lens group is used for secondarily displaying the three-dimensional image light field; the two-dimensional scanning galvanometer is used for changing the propagation direction of the three-dimensional image light field; the control unit is used for generating the pure phase hologram, loading the pure phase hologram to the spatial light modulator, and controlling the two-dimensional scanning galvanometer to change the propagation direction of the three-dimensional image light field.
In some embodiments, the projection device further comprises a diaphragm; the diaphragm is arranged on the focal plane of the first lens group and used for filtering stray light and allowing the three-dimensional image light field to pass through.
In some embodiments, the projection device further comprises a reflection unit; the reflecting unit is arranged between the first lens group and the second lens group and used for receiving the three-dimensional image light field emitted by the first lens group and reflecting the three-dimensional image light field to the second lens group.
In a fourth aspect, an embodiment of the present invention further provides a head-up display, including a windshield, an eye tracking unit, and the projection apparatus according to any one of the third aspects; the windshield is arranged in the light emitting direction of the projection device and used for reflecting the three-dimensional image light field to human eyes, the eye movement tracking unit is connected with the control unit and used for tracking the position information of the eyes of a user and sending the position information to the control unit; the control unit is used for controlling the two-dimensional scanning galvanometer to change the propagation direction of the three-dimensional image light field according to the received position information.
In some embodiments, the heads-up display includes a free-form mirror; the free-form surface reflector is arranged in the light emitting direction of the projection device, the windshield is arranged in the reflecting direction of the free-form surface reflector, and the free-form surface reflector is used for reflecting the three-dimensional image light field emitted by the projection device to the windshield.
In some embodiments, the heads-up display includes a volume holographic optical element; the volume holographic optical element is attached to the windshield and used for reflecting the three-dimensional image light field emitted by the projection device to human eyes.
In some embodiments, the heads-up display further comprises a radar and/or camera unit; the control unit is respectively connected with the radar and/or the camera shooting unit.
In a fifth aspect, the present invention also provides a computer-readable storage medium storing computer-executable instructions for causing a computer to perform the method according to the first aspect.
In a sixth aspect, the present invention also provides a computer program product, the computer program product comprising a computer program stored on a computer-readable storage medium, the computer program comprising program instructions which, when executed by a computer, cause the computer to perform the method of the first aspect.
Compared with the prior art, the invention has the beneficial effects that: in contrast to the prior art, an embodiment of the present invention provides a hologram generation method, a control unit, a projection apparatus, and a head-up display, where the method includes: step S100: acquiring an initial phase of a plane where a spatial light modulator is located, a focal length of a first lens group, n display depths of a three-dimensional image and image information of the three-dimensional image on the plane where the n display depths are located, wherein n is not less than 2 and is an integer; step S200: respectively obtaining a first complex amplitude corresponding to each display depth according to the focal length and the n display depths; step S300: calculating a first phase of a plane where the spatial light modulator is located according to a first complex amplitude corresponding to a kth display depth, image information on the plane where the kth display depth is located and an initial phase, and updating the initial phase to the first phase, wherein k is greater than or equal to 1 and less than or equal to n, and k is an integer; step S400: repeatedly executing the step S300 to finish the iterative process of calculating the first phase from the 1 st display depth to the nth display depth; step S500: and continuing to repeatedly execute the step S300 until the iteration process is completed for a preset number of times, and taking the finally obtained first phase as the pure-phase hologram to be loaded by the spatial light modulator. By generating the hologram through the method, the projection device can form images on multiple depths, 3D display is realized, and the depth range of the 3D display is improved.
Drawings
One or more embodiments are illustrated by the accompanying figures in the drawings that correspond thereto and are not to be construed as limiting the embodiments, wherein elements/modules and steps having the same reference numerals are represented by like elements/modules and steps, unless otherwise specified, and the drawings are not to scale.
Fig. 1 is a schematic structural diagram of a head-up display according to an embodiment of the invention;
FIG. 2 is a schematic diagram of another embodiment of a head-up display;
fig. 3 is a schematic structural diagram of a projection apparatus according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a control unit according to an embodiment of the present invention;
fig. 5 is an equivalent schematic diagram of a projection apparatus according to an embodiment of the invention;
FIG. 6 is a schematic flow chart of a hologram generating method according to an embodiment of the present invention;
fig. 7 is a schematic flowchart of a step S300 according to an embodiment of the present invention;
fig. 8 is a schematic flowchart of a step S310 according to an embodiment of the present invention;
FIG. 9 is a phase-only hologram provided by an embodiment of the present invention that uses a secondary phase as an initial phase;
FIG. 10 is a result of numerical reproduction at six display depths using a secondary phase as an initial phase according to an embodiment of the present invention;
FIG. 11 is a phase-only hologram using a random phase as an initial phase according to an embodiment of the present invention;
FIG. 12 is a numerical reproduction of results at six display depths using a random phase as an initial phase according to an embodiment of the present invention;
fig. 13 is a diagram of an actual display effect of the heads-up display of fig. 2.
Description of reference numerals: 100. a projection device, 200, an eye movement tracking unit, 300, a windshield, 400, a free-form surface mirror, 500, a human eye, a three-dimensional image generated by the projection device, a', a three-dimensional virtual image observed by the human eye, 600, a volume holographic optical element, 10, a spatial light modulator, 20, an illumination unit, 21, a light source, 22, a polarizing beam splitter, 30, a first lens group, 31, a first lens, 32, a second lens, 40, a second lens group, 41, a third lens, 42, a fourth lens, 43, a fifth lens, 44, a sixth lens, 45, a seventh lens, 50, a two-dimensional scanning galvanometer, 60, a control unit, 70, a diaphragm, 80, a reflection unit, 81, a first mirror, 82, a second mirror, 61, a processor, 62, a memory, S1, a plane of a first display depth, S2, a plane of a second display depth, S3, a plane of a third display depth, f. of 1 The focal length of the first lens group, d1, the distance between the plane of the first display depth and the plane of the second display depth, and d2, the distance between the plane of the second display depth and the plane of the third display depth.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.
In order to facilitate an understanding of the present application, the present application is described in more detail below with reference to the accompanying drawings and specific embodiments. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
It should be noted that, if not conflicted, the various features of the embodiments of the invention may be combined with each other within the scope of protection of the present application. In addition, although the functional blocks are divided in the device diagram, in some cases, the blocks may be divided differently from those in the device. Further, the terms "first," "second," and the like, as used herein, do not limit the data and the execution order, but merely distinguish the same items or similar items having substantially the same functions and actions.
To facilitate understanding of the present invention, first, a structure of a head-up display according to an embodiment of the present invention is described, and referring to fig. 1, the head-up display includes a projection apparatus 100, an eye tracking unit 200, and a windshield 300.
The windshield 300 is disposed in the light emitting direction of the projection apparatus 100, the windshield 300 is configured to reflect the three-dimensional image light field to the human eyes 500, the eye tracking unit 200 is connected to the projection apparatus 100, and the eye tracking unit 200 is configured to track the position information of the eyes of the user and send the position information of the eyes of the user to the projection apparatus 100.
The eye-tracking unit 200 may include a binocular camera system or a combination of an infrared laser transmitter and a single camera. The specific way of tracking the position information of the two eyes of the user can refer to the prior art, and is not limited herein.
In the head-up display, the position information of both eyes of the user is tracked by the eye-movement tracking unit 200 and transmitted to the projection apparatus 100; the projection device 100 executes the hologram generating method provided by the present invention to generate two phase-only holograms corresponding to the 3D images required for viewing by the left and right eyes, respectively, and to generate the 3D images required for viewing by the left and right eyes from the two phase-only holograms, respectively; finally, the projection device 100 sends out the 3D image light field with the 3D image information to the windshield 300 in time sequence according to the position information of the two eyes of the user, the windshield 300 reflects the 3D image light field to the human eyes 500 respectively, and the human eyes 500 can observe the 3D virtual image a' located far away through the windshield 300, so that the left eye and the right eye of the user can respectively see the 3D display effect corresponding to the parallax.
In some embodiments, referring to fig. 1, the head-up display includes a free-form surface mirror 400; the free-form surface reflector 400 is disposed in the light outgoing direction of the projection apparatus 100, the windshield 300 is disposed in the reflection direction of the free-form surface reflector 400, and the free-form surface reflector 400 is used for reflecting the three-dimensional image light field emitted from the projection apparatus 100 to the windshield 300. By arranging the free-form surface reflector 400, the surface of the free-form surface reflector 400 is optimally designed, so that the three-dimensional image light field emitted by the projection device 100 can be shaped, and the display quality is improved.
In some embodiments, referring to FIG. 2, a heads-up display includes a volume holographic optical element 600; the volume holographic optical element 600 is attached to the windshield 300, and the volume holographic optical element 600 is used for reflecting the three-dimensional image light field emitted by the projection device to human eyes. In the head-up display, a three-dimensional image light field emitted from the projection apparatus 100 may be reflected by the volume hologram optical element 600 to the human eye 500. By optimally designing the volume holographic optical element 600, the three-dimensional image light field emitted by the projection device 100 can be shaped, and the display effect is improved. Specifically, the volume hologram optical element 600 may be a volume hologram lens, which can be used to correct aberration and can be manufactured by exposing a photosensitive material, which may be a silver salt material, a photopolymer, or the like, by interference of a divergent spherical wave and a convergent spherical wave, without limitation. In practical applications, the volume hologram optical element may be a single-chip monochrome display volume hologram optical element, a single-chip full-color display volume hologram optical element, or a multi-chip combined volume hologram optical element that can be used for full-color display, which is not limited herein.
In some of these embodiments, the heads-up display further comprises a radar and/or camera unit; the projection device is respectively connected with the radar and/or the camera unit. The radar can be vehicle-mounted radar, the camera shooting unit can comprise a plurality of cameras, the radar and/or the camera shooting unit can acquire environmental information of a current driving scene and send the environmental information to the projection device, the projection device can generate 3D images needing to be observed according to the environmental information subsequently, the corresponding parallax can be seen by left and right eyes of a user respectively subsequently, the images are displayed in an AR-3D mode, the images are fused with the current driving environment, and AR-3D display is achieved.
An embodiment of the present invention further provides an implementation manner of a projection apparatus 100, please refer to fig. 3, in which the projection apparatus 100 includes: an illumination unit 20, a spatial light modulator 10, a first lens group 30, a second lens group 40, a two-dimensional scanning galvanometer 50, and a control unit 60.
The spatial light modulator 10 is arranged in the light-emitting direction of the illumination unit 20, the first lens group 30, the second lens group 40 and the two-dimensional scanning galvanometer 50 are sequentially arranged in the light-emitting direction of the spatial light modulator 10, the spatial light modulator 10 is arranged on the front focal plane of the first lens group 30, and the control unit 60 is respectively connected with the spatial light modulator 10 and the two-dimensional scanning galvanometer 50; wherein the illumination unit 20 is used for generating illumination light; the spatial light modulator 10 is used for loading a pure phase hologram and modulating the received illumination light according to the pure phase hologram to generate a three-dimensional image light field; the first lens group 30 is used for displaying a three-dimensional image light field once; the second lens group 40 is used for carrying out secondary display on the three-dimensional image light field; the two-dimensional scanning galvanometer 50 is used for changing the propagation direction of the three-dimensional image light field; the control unit 60 is used to generate phase-only holograms and load them into the spatial light modulator 10, and to control the two-dimensional scanning galvanometer 50 to change the propagation direction of the three-dimensional image light field.
The spatial light modulator 10 is a reflective phase-only spatial light modulator LCoS.
The first lens group 30 may include a first lens 31 and a second lens 32, and the second lens group 40 may include a third lens 41, a fourth lens 42, a fifth lens 43, a sixth lens 44, and a seventh lens 45. The number and type of the lenses of the first lens group 30 and the second lens group 40 may be optimized by optical design and are not limited thereto.
Specifically, in the projection apparatus 100, the control unit 60 is configured to execute the hologram generating method according to the embodiment of the present invention, and is capable of generating a pure-phase hologram, loading the pure-phase hologram into the spatial light modulator 10, modulating the received illumination light to generate a 3D image light field after the pure-phase hologram is loaded into the spatial light modulator 10, wherein the 3D image light field generated after modulation is once displayed by the first lens group 30, and is capable of forming a plurality of images on a plane at a plurality of depths near the focal plane of the first lens group 30 to form a 3D image (the 3D image is a real image), and the 3D image light field continuously passes through the second lens group 40, and the second lens group 40 is capable of continuously displaying the 3D image light field for a second time, i.e. amplifying the 3D image formed by the first lens group 30 to form a projected light field, the projected light field is directed in different directions by the two-dimensional scanning galvanometer 50 and subsequently can enter the human eye.
When the projection apparatus 100 is applied to a head-up display, the control unit 60 may be connected to the eye tracking unit and further connected to the radar and/or the camera unit, and the control unit 60 may first obtain the environmental information according to the radar and/or the camera unit, and generate the 3D images that the left and right eyes of the user respectively need to observe according to the environmental information; then, the control unit 60 executes the hologram generating method provided by the present invention to generate two pure phase holograms corresponding to the 3D images required by the left and right eyes respectively, and loads the two pure phase holograms to the spatial light modulator 10, so that the spatial light modulator 10 can modulate the illumination light and emit a three-dimensional image light field with 3D image information, and the three-dimensional image light field generates the 3D image after being sequentially displayed by the first lens group 30 and the second lens group 40; in addition, the control unit 60 controls the two-dimensional scanning galvanometer 50 to change the propagation direction of the light field of the three-dimensional image according to the position information of the two eyes of the user acquired by the eye movement tracking unit, specifically, controls the two-dimensional scanning galvanometer 50 to deflect the projection light in time sequence according to the position information of the two eyes of the user acquired by the eye movement tracking unit, and finally enables the projection light to enter the left eye and the right eye of the person in time sequence, so that the AR-3D display image can be observed by the eyes of the person through persistence of vision.
In some embodiments, referring to fig. 3, the projection apparatus 100 further includes a diaphragm 70; the diaphragm 70 is disposed on the focal plane of the first lens group 30, and the diaphragm 70 is disposed between the first lens group 30 and the second lens group 40, the diaphragm 70 is used for filtering stray light and allowing the three-dimensional image light field to enter the subsequent optical system. By providing the aperture 70, stray light such as high-order diffracted light can be removed, and the display effect can be improved.
In some embodiments, referring to fig. 3, the projection apparatus 100 further includes a reflection unit 80; the reflection unit 80 is disposed between the first lens group 30 and the second lens group 40, and the reflection unit 80 is configured to receive the three-dimensional image field emitted from the first lens group 30 and reflect the three-dimensional image field to the second lens group 40. Specifically, referring to fig. 3, the reflection unit 80 includes a first reflector 81 and a second reflector 82, the first reflector 81 is disposed in the light-emitting direction of the first lens group 30, the second reflector 82 is disposed in the reflection direction of the first reflector 81, and the light-entering direction of the second lens group 40 is disposed in the reflection direction of the second reflector 82. By providing the first reflecting mirror 81 and the second reflecting mirror 82, the light path can be folded, and the space utilization of the projection apparatus 100 can be improved.
In some embodiments, referring to fig. 3, the illumination unit 20 includes a light source 21. The light source 21 may be a monochromatic laser, or a combination of multiple lasers and dichroic mirrors. When a three-color laser is used as a light source, full-color display can be realized by time-sequential color illumination.
In some embodiments, the illumination unit 20 further includes a polarization beam splitter prism 22, wherein the light source 21 is disposed on a first side of the polarization beam splitter prism 22, the spatial light modulator 10 is disposed on a second side of the polarization beam splitter prism 22, and the first lens group 30 is disposed on a third side of the polarization beam splitter prism 22 opposite to the first side. In this embodiment, the illumination light emitted from the light source 21 is reflected to the spatial light modulator 10 through the polarization beam splitter prism 22, and the spatial light modulator 10 receives the illumination light and emits a three-dimensional image light field with three-dimensional image information to the polarization beam splitter prism 22, and the three-dimensional image light field is transmitted to the first lens group 30 through the polarization beam splitter prism 22. In practical applications, the polarization splitting prism 22 can be omitted by using a light source to tilt off-axis to illuminate the spatial light modulator 10, and the first lens group 30 and the second lens group 40 are sequentially disposed in the direction of the reflected light of the spatial light modulator 10.
In some embodiments, the illumination unit 20 further includes a collimating lens and a pinhole filter, which may be sequentially disposed between the light source 21 and the polarization splitting prism 22, wherein the collimating lens is used for collimating the illumination light, and the pinhole filter is used for filtering the illumination light.
Referring to fig. 4, it shows a hardware structure of a control unit 60 for executing the hologram generating method provided by the present invention, where the control unit 60 may be the control unit 60 shown in fig. 3, and specifically, the control unit 60 includes: at least one processor; and a memory communicatively coupled to the at least one processor; wherein the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the hologram generation method according to any one of the first aspect. The processor 61 and the memory 62 may be connected by a bus or other means, and fig. 4 illustrates the connection by a bus as an example.
The memory 62, which is a non-volatile computer-readable storage medium, may be used to store non-volatile software programs, non-volatile computer-executable programs, and modules, such as program instructions/modules corresponding to the hologram generation method in the embodiments of the present invention. The processor 61 executes various functional applications of the server and data processing by executing nonvolatile software programs, instructions, and modules stored in the memory 62, that is, implements the hologram generation method described in the method embodiments described below.
The memory 62 may include a storage program area and a storage data area, wherein the storage program area may store an operating system, an application program required for at least one function; the storage data area may store data created according to use of the processor, and the like. Further, the memory 62 may include high speed random access memory, and may also include non-volatile memory, such as at least one magnetic disk storage device, flash memory device, or other non-volatile solid state storage device. In some of these embodiments, the memory 62 optionally includes memory located remotely from the processor 61, and these remote memories may be connected to the processor via a network. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.
The one or more modules are stored in the memory 62 and when executed by the one or more processors 61 perform the hologram generation method in any of the method embodiments described below.
The product can execute the method provided by the embodiment of the invention, and has corresponding functional modules and beneficial effects of the execution method. For technical details that are not described in detail in this embodiment, reference may be made to the method provided by the embodiment of the present invention.
The hologram generating method according to an embodiment of the present invention is described in detail below with reference to the accompanying drawings, and is applied to a projection apparatus according to any one of the above embodiments, where the projection apparatus is equivalent to the model shown in fig. 5, and the projection apparatus includes a spatial light modulator 10 and a first lens group 30, and the spatial light modulator 10 is disposed on a front focal plane of the first lens group 30, and the method can be executed by a control unit according to any one of the above embodiments, please refer to fig. 5 and 6, and the method includes:
step S100: acquiring an initial phase of a plane where the spatial light modulator is located, a focal length of the first lens group, n display depths of the three-dimensional image and image information of the three-dimensional image on the plane where the n display depths are located, wherein n is not less than 2 and is an integer;
the spatial light modulator 10 is also in the plane of the hologram. The initial phase of the plane in which the spatial light modulator 10 is located includes a random phase or a quadratic phase. When random phase is used, initial phase
Can be expressed as:
wherein rand (M, N) is a random number between 0 and 1 for generating an M × N; m and N are the resolution of the hologram, e.g. M may be 1080 and N may be 1920.
When the initial phase adopts the secondary phase, the initial phase can be expressed as:
where α and β are coefficients, respectively, and (x, y) are coordinates on a plane on which the hologram is located.
The three-dimensional image is a three-dimensional image formed by the first lens group 10 after the spatial light modulator 10 modulates the illumination light according to the loaded phase-only hologram, and the three-dimensional image can be divided into image information on a plane where n display depths are located. At this time, referring to fig. 5, a depth coordinate axis can be established with the focal plane S2 of the first lens group 30 as the origin, perpendicular to the focal plane S2 of the first lens group 30 and in the positive direction toward the first lens group 30 as the positive direction. The n display depths may be a plurality of continuous depths or a plurality of discontinuous depths, and may be set according to actual needs in practical applications, which is not limited herein.
Step S200: respectively obtaining a first complex amplitude corresponding to each display depth according to the focal length and the n display depths;
specifically, in some embodiments, the first complex amplitude corresponding to the kth display depth is
wherein ,
z k is the k display depth of the three-dimensional image, lambda is the wavelength, f 1 Is composed ofThe focal length (x, y) of the first lens group is a coordinate on the plane where the spatial light modulator 10 is located. Wherein k is more than or equal to 1 and less than or equal to n, and k is an integer.
Step S300: calculating a first phase of a plane where the spatial light modulator is located according to the first complex amplitude corresponding to the kth display depth, the image information on the plane where the kth display depth is located and an initial phase, and updating the initial phase to the first phase, wherein k is greater than or equal to 1 and less than or equal to n, and is an integer;
specifically, the initial phase is constrained by the image information on the plane of the kth display depth, so that the first phase of the plane of the spatial light modulator 10 can be optimized, and the subsequent spatial light modulator 10 can load according to the first phase and modulate the illumination light, and then can display on the plane of the kth display depth.
Step S400: repeatedly executing the step S300, and completing an iterative process of calculating the first phase from the 1 st display depth to the nth display depth;
by repeatedly executing step S300, the constrained optimization of the first phase from the 1 st display depth to the nth display depth can be completed, so that the subsequent spatial light modulator 10 can perform the loading according to the first phase and perform the modulation on the illumination light, and then can perform the display on the plane where the 1 st display depth to the nth display depth are located.
Step S500: and continuing to repeatedly execute the step S300 until the iteration process is completed for a preset number of times, and taking the finally obtained first phase as a pure phase hologram to be loaded by the spatial light modulator.
In the hologram calculation method provided in this embodiment, a three-dimensional image is divided into image information on a plane where multiple depths are located, and optimization iteration is performed on an initial phase by using the image information on the plane where multiple display depths are located, where in one iteration process, n sets of diffraction calculations from the plane where the spatial light modulator is located to a spectrum plane and from the spectrum plane to the plane where the spatial light modulator is located are included, and thus, after multiple rounds of iterations, an obtained first phase can be used as a pure phase hologram to be loaded by the spatial light modulator. The subsequent spatial light modulator can modulate the illumination light according to the pure phase hologram to emit a light field with three-dimensional image information, and the light field can be respectively displayed on a plurality of depth planes near a focal plane after passing through the first lens group, so that three-dimensional display is realized, and the depth range of the three-dimensional display is improved.
Specifically, in some embodiments, referring to fig. 7, the step S300 includes:
step S310: and obtaining a second complex amplitude of the plane where the spatial light modulator is located according to the initial phase and the first complex amplitude corresponding to the kth display depth.
In one embodiment, referring to fig. 8, the step S310 may include:
step S311: obtaining a fourth complex amplitude of the plane where the spatial light modulator is located according to the initial phase;
step S312: and obtaining the second complex amplitude according to the conjugate of the first complex amplitude corresponding to the kth display depth and the fourth complex amplitude.
In particular, the initial phase is obtained
Then, a fourth complex amplitude of the plane of the spatial light modulator can be obtained as
The first complex amplitude corresponding to the kth display depth is
Then the conjugate of the first complex amplitude corresponding to the kth display depth is
Then, the second complex amplitude is
Step S320: performing two-dimensional Fourier transform on the second complex amplitude to obtain a frequency spectrum corresponding to the second complex amplitude;
then, for the second complex amplitude
Performing two-dimensional Fourier transform to obtain a frequency spectrum corresponding to the second complex amplitude
wherein ,
the representation is a two-dimensional fourier transform of.
Step S330: and performing weight superposition on the image information on the plane where the kth display depth is located and the amplitude of the frequency spectrum, and reserving the phase of the frequency spectrum to obtain the frequency spectrum after weight.
In one specific embodiment, the step S330 may include: obtaining the weighted spectrum F by the following formula zk ′：
wherein ,
A zk ＝|F zk |/max{|F zk |}；
P k is the image information on the plane of the kth display depth, epsilon is the weight factor corresponding to the image information on the plane of the kth display depth, | F zk | is the frequency spectrum F zk Modulo of (max { | F) zk Denotes a pair | F zk L maximum, angle { F |) zk Denotes a pair F zk And taking the phase. A. the zk Representing a normalized amplitude.
Specifically, epsilon is any number between 0 and 1, and preferably epsilon is 1/n, so that the display effect of the three-dimensional image on the plane where each display depth is located can be improved. The image information on the plane of the kth display depth may be amplitude information of the image on the plane of the kth display depth.
Step S340: and performing two-dimensional inverse Fourier transform on the weighted frequency spectrum to obtain a third complex amplitude on the plane where the spatial modulator is located.
In particular, for the weighted spectrum F zk ' after performing two-dimensional inverse Fourier transform, a third complex amplitude can be obtained as
wherein ,
the representation is a two-dimensional inverse fourier transform.
Step S350: and obtaining the first phase according to the third complex amplitude and the first complex amplitude corresponding to the kth display depth, and updating the initial phase to the first phase.
In particular, the first phase may be
Wherein angle { } denotes taking the phase of pair, and updating the initial phase to, i.e.
In this embodiment, through the above calculation, a set of diffraction calculations from the plane where the spatial light modulator is located to the focal plane and from the focal plane to the plane where the spatial light modulator is located can be performed.
The hologram generating method provided by the embodiment of the present invention is described in detail below with reference to specific embodiments. Illustratively, three depths may be selected, each being a first display depth z 1 A second display depth z 2 And a third display depth z 3 Please refer to fig. 5, the planes of the first display depth z are 1 On the plane S1 thTwo display depth z 2 Lying plane S2 and third display depth z 3 At the plane S3, the first display depth z 1 D1, the second display depth z 2 Is 0, third display depth z 3 Is-d 2, and d1 is the first display depth z 1 The plane S1 and the second display depth z 2 The distance between the planes S2, d2 is the second display depth z 2 The plane S2 and the third display depth z 3 The distance of the lying plane S3.
First, according to the initial phase
A first display depth z 1 Corresponding first complex amplitude
Conjugation of (2)
Obtaining a second complex amplitude in the plane of the spatial light modulator 10 of
And performing two-dimensional Fourier transform on the spectrum to obtain a first frequency spectrum
Reusing the image information P corresponding to the first display depth 1 Weight superposition with the amplitude of the first frequency spectrum, and reserving the phase of the first frequency spectrum to obtain the weighted frequency spectrum
Wherein, the epsilon is 1/3,
A z1 ＝|F z1 |/max{|F z1 |}；
then, two-dimensional inverse Fourier transform is carried out on the weighted frequency spectrum to obtain spaceA third complex amplitude distribution in the plane of the optical modulator is
Then, the first phase can be obtained as
And will initiate the phase
Is updated to the first phase, i.e.
Then, according to the updated initial phase
Second display depth z 2 Corresponding first complex amplitude
Conjugation of (2)
Obtaining a second complex amplitude in the plane of the spatial light modulator 10 of
And performing two-dimensional Fourier transform on the spectrum to obtain a second frequency spectrum
Reusing the image information P corresponding to the second display depth 2 Weight superposition with the amplitude of the second frequency spectrum, and reserving the phase of the second frequency spectrum to obtain the weighted frequency spectrum
Wherein, the epsilon is 1/3,
A z2 ＝|F z2 |/max{|F z2 |}；
then, the weighted spectrum is subjected to two-dimensional inverse fourier transform to obtain a third complex amplitude distribution on the plane where the spatial light modulator 10 is located
Then, the first phase can be obtained as
And will be in the initial phase
Is updated to the first phase, i.e.
Then, according to the updated initial phase
Third display depth z 3 Corresponding first complex amplitude
Conjugation of (2)
Obtaining a second complex amplitude in the plane of the spatial light modulator 10 of
And performing two-dimensional Fourier transform on the spectrum to obtain a third spectrum
Reusing the image information P corresponding to the third display depth 3 Weight superposition with the amplitude of the third frequency spectrum, and reserving the phase of the third frequency spectrum to obtain the weighted frequency spectrum
Wherein, the epsilon is 1/3,
A z3 ＝|F z3 |/max{|F z3 |}；
then, the weighted spectrum is subjected to two-dimensional inverse fourier transform to obtain a third complex amplitude distribution on the plane where the spatial light modulator 10 is located
Then, a first phase of
And will initiate the phase
Is updated to the first phase, i.e.
After the above calculation is completed, an iterative process of calculating the first phase from the 1 st display depth to the 3 rd display depth is completed, that is, the diffraction calculation including 3 sets from the plane where the spatial light modulator 10 is located to the spectral plane and from the spectral plane to the plane where the spatial light modulator 10 is located is completed. Then, carrying out an iterative process of calculating a first phase for the next time from the 1 st display depth to the 3 rd display depth, and taking the finally obtained first phase as a pure phase hologram to be loaded by the spatial light modulator after the iterative process meets the preset times, namely the pure phase hologram is
It will be appreciated that when the phase-only hologram is obtained, the 1 st reconstructed image at the display depth is
The 2 nd display depth is
The 3 rd display depth is
Please refer to fig. 9 to 12. Wherein, fig. 9 and 11 are pure phase holograms obtained by iterative computation using a random phase and a secondary phase as initial phases, respectively, and fig. 10 and 12 are results of numerical reconstruction of the pure phase holograms in fig. 9 and 11 at six display depths, respectively, from which it can be seen that when a certain depth image is displayed, the image at the depth is clear, and images at other depths are blurred due to defocusing, proving that the proposed algorithm realizes display of a multi-depth three-dimensional image. In the calculation, six display depths of [ -5mm, -3mm,0mm,3mm, 5mm, 8mm ], a focal length of the first lens group of 100mm, a wavelength λ of 532nm, and ∈ 1/6, a preset number of times of 100 times, a hologram resolution of mxn 1080 × 1920, an α of the secondary phase of 0.0028, and a β of the secondary phase of 0.3 are selected as parameters for calculation. As can be seen from fig. 9 to 12, the phase-only hologram calculated using the secondary phase as the initial phase has better phase continuity, so that speckle noise of the reconstructed image is suppressed, and the phase-only hologram calculated using the random phase as the initial phase has a smaller depth of focus of the reconstructed image, so that the reconstructed image has a more obvious defocus effect.
Next, referring to fig. 13, fig. 13 is a diagram of an actual display effect after the control unit in the projection apparatus executes the hologram generating method according to the present invention, and the embodiment shown in fig. 2 is adopted. The projection device includes an illumination unit, a phase-only spatial light modulator (e.g., LCoS), a first lens set, a diaphragm, a second lens set, and a volume hologram optical element, and the specific configuration thereof is described above and will not be described herein again. In the calculation process, three display depths of [ -3mm,0mm and 3mm ], the focal length of the first lens group is 100mm, the wavelength lambda is 532nm, the weight factor 1/3 and the preset times are 100, and the initial phase is the random phase and other parameters are adopted for calculation. The display depths after the amplification by the second projection lens and the volume holographic optical element are respectively about: 2m, 2.5m and 3 m. Fig. 13 (a) is a display focused on a display depth of 2m, fig. 13 (b) is a display focused on a display depth of 2.5m, and fig. 13 (c) is a display focused on a display depth of 3 m. As can be seen from fig. 13, when the camera focuses on a certain depth image, the other two depths are blurred due to defocusing, and multi-depth holographic 3D display is realized; in addition, the volume holographic optical element used by the projection device has better transparency, so that a rear object can be observed through the volume holographic element, and the rear object can also present a fuzzy state due to different focusing depths.
In summary, the hologram generating method provided by the embodiment of the invention is applied to a projection apparatus, and can generate images at a plurality of display depths, thereby forming a 3D image, realizing 3D display, and improving the display depth range.
Embodiments of the present invention also provide a non-transitory computer-readable storage medium storing computer-executable instructions for execution by one or more processors, e.g., to perform the method steps of fig. 6-8 described above.
Embodiments of the present invention also provide a computer program product comprising a computer program stored on a non-transitory computer readable storage medium, the computer program comprising program instructions which, when executed by a computer, cause the computer to perform a hologram generation method in any of the method embodiments described above, for example, to perform the method steps of fig. 6 to 8 described above.
It should be noted that the above-described device embodiments are merely illustrative, where the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment.
Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented by software plus a general hardware platform, and certainly can also be implemented by hardware. Based on such understanding, the above technical solutions substantially or otherwise contributing to the related art may be embodied in the form of a software product, which may be stored in a computer-readable storage medium, such as ROM/RAM, magnetic disk, optical disk, etc., and includes a plurality of instructions for executing the method according to each embodiment or some parts of the embodiments by at least one computer device (which may be a personal computer, a server, or a network device, etc.).
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; within the idea of the invention, also technical features in the above embodiments or in different embodiments may be combined, steps may be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (14)
1. A hologram generation method is applied to a projection device, wherein the projection device comprises a spatial light modulator and a first lens group, the spatial light modulator is arranged on a front focal plane of the first lens group, the spatial light modulator is used for loading a hologram and modulating received illumination light according to the hologram to generate a three-dimensional image light field, and the first lens group is used for displaying the three-dimensional image light field to form a three-dimensional image;
the method comprises the following steps:
step S100: acquiring an initial phase of a plane where the spatial light modulator is located, a focal length of the first lens group, n display depths of the three-dimensional image and image information of the three-dimensional image on the plane where the n display depths are located, wherein n is not less than 2 and is an integer;
step S200: respectively obtaining a first complex amplitude corresponding to each display depth according to the focal length and the n display depths;
step S300: calculating a first phase of a plane where the spatial light modulator is located according to the first complex amplitude corresponding to the kth display depth, the image information on the plane where the kth display depth is located and an initial phase, and updating the initial phase to the first phase, wherein k is greater than or equal to 1 and less than or equal to n, and is an integer;
step S400: repeatedly executing the step S300 to finish one iteration process of calculating the first phase from the 1 st display depth to the nth display depth;
step S500: and continuing to repeatedly execute the step S300 until the iteration process is completed for a preset number of times, and taking the finally obtained first phase as a pure phase hologram to be loaded by the spatial light modulator.
2. The hologram generating method according to claim 1, wherein the initial phase of the plane in which the spatial light modulator is located includes a random phase or a quadratic phase.
3. The hologram generation method according to claim 2, wherein the step S300 includes:
step S310: obtaining a second complex amplitude of the plane where the spatial light modulator is located according to the initial phase and the first complex amplitude corresponding to the kth display depth;
step S320: performing two-dimensional Fourier transform on the second complex amplitude to obtain a frequency spectrum corresponding to the second complex amplitude;
step S330: carrying out weight superposition on the image information on the plane where the kth display depth is located and the amplitude of the frequency spectrum, and reserving the phase of the frequency spectrum to obtain the frequency spectrum after weight;
step S340: performing two-dimensional inverse Fourier transform on the weighted frequency spectrum to obtain a third complex amplitude on the plane where the spatial modulator is located;
step S350: and obtaining the first phase according to the third complex amplitude and the first complex amplitude corresponding to the kth display depth, and updating the initial phase to the first phase.
4. The hologram generating method according to claim 3, wherein the step S310 comprises:
step S311: obtaining a fourth complex amplitude of the plane where the spatial light modulator is located according to the initial phase;
step S312: and obtaining the second complex amplitude according to the conjugate of the first complex amplitude corresponding to the kth display depth and the fourth complex amplitude.
5. The hologram generation method according to claim 3, wherein the step S330 comprises:
obtaining the weighted spectrum F by the following formula zk ′：
wherein ,
A zk ＝|F zk |/max{|F zk |}；
P k is the image information on the plane of the kth display depth, epsilon is the weight factor corresponding to the image information on the plane of the kth display depth, | F zk Is the frequency spectrum F zk Modulo of (max { | F) zk Denotes the pair | F zk I solveMaximum value, angle { F } zk Denotes a pair F zk And taking the phase.
6. The hologram generating method according to any of claims 1 to 5, wherein said first complex amplitude for a kth display depth is
wherein ,
z k is the k display depth of the three-dimensional image, lambda is the wavelength, f 1 Is the focal length of the first lens group, (x, y) is the coordinate on the plane where the spatial light modulator is located.
7. A control unit, comprising:
at least one processor; and the number of the first and second groups,
a memory communicatively coupled to the at least one processor; wherein,
the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the hologram generation method according to any one of claims 1 to 6.
8. A projection device, comprising: an illumination unit, a spatial light modulator, a first lens group, a second lens group, a two-dimensional scanning galvanometer, and the control unit of claim 7;
the spatial light modulator is arranged in the light emergent direction of the illuminating unit, the first lens group, the second lens group and the two-dimensional scanning galvanometer are sequentially arranged in the light emergent direction of the spatial light modulator, the spatial light modulator is arranged on a front focal plane of the first lens group, and the control unit is respectively connected with the spatial light modulator and the two-dimensional scanning galvanometer;
wherein the illumination unit is used for generating illumination light; the spatial light modulator is used for loading the pure phase hologram and modulating the received illumination light according to the pure phase hologram so as to generate a three-dimensional image light field; the first lens group is used for displaying the three-dimensional image light field once; the second lens group is used for carrying out secondary display on the three-dimensional image light field; the two-dimensional scanning galvanometer is used for changing the propagation direction of the three-dimensional image light field; the control unit is used for generating the pure phase hologram, loading the pure phase hologram to the spatial light modulator, and controlling the two-dimensional scanning galvanometer to change the propagation direction of the three-dimensional image light field.
9. The projection device of claim 8, wherein the projection device further comprises a diaphragm;
the diaphragm is arranged on the focal plane of the first lens group and used for filtering stray light and allowing the three-dimensional image light field to pass through.
10. The projection device of claim 9, wherein the projection device further comprises a reflective unit;
the reflecting unit is arranged between the first lens group and the second lens group and used for receiving the three-dimensional image light field emitted by the first lens group and reflecting the three-dimensional image light field to the second lens group.
11. A heads-up display comprising a windscreen, an eye tracking unit, and a projection device according to any one of claims 8-10;
the windshield is arranged in the light emergent direction of the projection device and used for reflecting the light field of the three-dimensional image to human eyes, the eye movement tracking unit is connected with the control unit and used for tracking the position information of the eyes of the user and sending the position information to the control unit; the control unit is used for controlling the two-dimensional scanning galvanometer to change the propagation direction of the three-dimensional image light field according to the received position information.
12. The heads-up display of claim 11 wherein the heads-up display includes a free-form mirror;
the free-form surface reflector is arranged in the light emitting direction of the projection device, the windshield is arranged in the reflecting direction of the free-form surface reflector, and the free-form surface reflector is used for reflecting the three-dimensional image light field emitted by the projection device to the windshield.
13. The heads-up display of claim 11 wherein the heads-up display includes a volume holographic optical element;
the volume holographic optical element is attached to the windshield and used for reflecting the three-dimensional image light field emitted by the projection device to human eyes.
14. The heads-up display of any one of claims 11-13 further comprising a radar and/or camera unit;
the control unit is respectively connected with the radar and/or the camera shooting unit.
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