CN113109945A

CN113109945A - Waveguide display device

Info

Publication number: CN113109945A
Application number: CN202110401306.8A
Authority: CN
Inventors: 张莉
Original assignee: Anhui Zhongke Grating Technology Co ltd
Current assignee: Anhui Zhongke Grating Technology Co ltd
Priority date: 2021-04-14
Filing date: 2021-04-14
Publication date: 2021-07-13

Abstract

The invention discloses a waveguide display device, comprising: an illumination unit for providing a light source image; the DLP projection unit is used for outputting light source images with uneven brightness; the coupling unit is used for converting the light source image with uneven brightness into a light source image with even brightness; wherein, lighting unit, DLP projection unit and coupling unit dock in proper order. The brightness of the output image can be made uniform. The invention is applied to the technical field of optical devices.

Description

Waveguide display device

Technical Field

The invention relates to the technical field of optical devices, in particular to a waveguide display device.

Background

Augmented Reality (AR) technology is a new technology that integrates real world information and virtual world information "seamlessly," allowing users to both immerse in the real world and accept information provided by AR devices. Optical see-through devices have been widely used in recent years in fields such as navigation, education, entertainment, military, and biomedical applications as mainstream augmented reality display schemes.

The scheme for realizing the optical perspective display is a traditional refraction/reflection optical system based on the geometrical optics principle, but the system has the problems of small exit pupil range, overlarge volume and the like, and does not meet the market requirement. To address these problems, waveguide-based optical system display schemes have been devised. The slab waveguide can provide a more compact and light structure, and also provides great convenience for the exit pupil expansion, and the light can directly expand the exit pupil along the propagation direction inside the waveguide, thereby further improving the display performance. However, during the propagation of the light along the pupil expanding direction, the energy of the light gradually attenuates with the step output, and finally the brightness of the virtual image received by the human eye is uneven, so that the user experience feels the influence.

Disclosure of Invention

Technical problem to be solved

A waveguide display device solves the technical problem of uneven image brightness output by a traditional flat waveguide.

(II) technical scheme

To solve the above technical problem, the present invention provides a waveguide display device, comprising:

an illumination unit for providing a light source image;

the DLP projection unit is used for outputting light source images with uneven brightness;

the coupling unit is used for converting the light source image with uneven brightness into a light source image with even brightness;

wherein, lighting unit, DLP projection unit and coupling unit dock in proper order.

In a further improvement, the illumination unit comprises an image source, a first lens and a second lens which are sequentially connected in an abutting mode, and the second lens is connected with the DLP projection unit in an abutting mode.

In a further improvement, the image source comprises at least two colors, and the image source of each color is respectively and correspondingly provided with a DLP projection unit and a coupling unit.

In a further refinement, the image source comprises three colors of red, green and blue.

In a further improvement, the DLP projection unit includes a TIR prism and an optical modulation device, and the illumination unit, the TIR prism, the optical modulation device and the coupling unit are sequentially connected in an abutting manner.

The improved optical fiber laser device further comprises a computer, a third lens, a fourth lens and a CCD camera, wherein the fourth lens is positioned between the optical modulator and the CCD camera, the third lens, the optical modulator, the fourth lens and the CCD camera sequentially form optical path connection, and the CCD camera and the optical modulation device are electrically connected with the computer respectively.

In a further improvement, the coupling unit comprises a slab waveguide, and an input coupling element and an output coupling element which are arranged on the slab waveguide, and the illumination unit, the DLP projection unit, the input coupling element and the output coupling element are sequentially butted.

In a further improvement, the input coupling element is one of a binary rectangular grating, an inclined grating and a blazed grating;

the output coupling element is a two-dimensional grating.

In a further improvement, the two-dimensional grating is cylindrical or rectangular or hexagonal.

(III) advantageous effects

The unmodulated light beam has uniform brightness before encountering the coupling unit, but after encountering the coupling unit, the light beam energy is inevitably and gradually lost due to multiple diffraction, so that the brightness of the output light beam is gradually reduced along the pupil expanding direction, and a virtual image from light to dark is received by human eyes.

Therefore, in the waveguide display device of the present invention, after the light source image emitted by the illumination unit is emitted to the DLP projection unit, the DLP projection unit performs light supplement adjustment on the received light source image in advance according to the decreasing rule of the light source image output by the coupling unit, so that the DLP projection unit is a light source image with uneven brightness, and when the light source image is output by the coupling unit, the light source image with uneven brightness becomes light with even brightness, and human eyes receive the light source image with even brightness.

Drawings

FIG. 1 is a schematic structural diagram of a waveguide display device according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of a waveguide display device with three image sources 11 according to an embodiment of the present invention;

fig. 3 is a connection diagram of the computer, the third lens, the fourth lens, the optical modulation device and the CCD camera according to an embodiment of the present invention.

Detailed Description

The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed in a particular orientation, and be operated, and thus are not to be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

Referring to fig. 1 to 3, a waveguide display device includes:

a lighting unit 1 for providing a light source image;

a DLP projection unit 2 for outputting a light source image having uneven brightness;

a coupling unit 3 for converting the light source image with non-uniform brightness into a light source image with uniform brightness;

wherein, lighting unit 1, DLP projection unit 2 and coupling unit 3 dock in proper order.

The unmodulated light beam has a uniform brightness before encountering the coupling unit 3, but after encountering the coupling unit 3, the light beam energy is inevitably gradually lost due to multiple diffraction, so that the brightness of the output light beam is gradually reduced along the pupil expanding direction, and a virtual image from light to dark is received by human eyes.

Therefore, in the waveguide display device of this embodiment, after the light source image emitted by the illumination unit 1 is emitted to the DLP projection unit 2, the DLP projection unit 2 performs light supplement adjustment on the received light source image in advance according to the decreasing rule of the light source image output by the coupling unit 3, so that the DLP projection unit 2 is a light source image with uneven brightness, when the light source image is output by the coupling unit 3, the light source image with uneven brightness becomes light with even brightness, and the human eye 4 receives the light source image with even brightness.

Further, in an embodiment, the illumination unit 1 comprises an image source 11, a first lens 12 and a second lens 13 which are sequentially interfaced, and the second lens 13 is interfaced with the DLP projection unit 2. The image source 11 is used for emitting a light source image, and the first lens 12 and the second lens 13 are combined for performing expanded beam collimation on the light source image.

Further, in an embodiment, the image sources 11 include at least two colors, and each image source 11 of each color is correspondingly provided with one DLP projection unit 2 and one coupling unit 3. The image sources 11 of various colors can be mutually overlapped to generate a combined effect, thereby realizing color display.

Further, in one embodiment, the image source 11 includes three colors of red, green, and blue. Specifically, the image source 11 is a red, green, and blue LED or a red, green, and blue monochromatic laser.

Further, in an embodiment, the DLP projection unit 2 includes a TIR prism 21 and an optical modulation device 22, and the illumination unit 1, the TIR prism 21, the optical modulation device 22 and the coupling unit 3 are sequentially connected in an interface.

The optical modulation device 22 is abbreviated as DMD, and the optical modulation device 22 can intelligently reflect an incident image light source, thereby creating an image; and the light source of the re-image is introduced into the slab waveguide 31 of the coupling unit 3. The DMD, the most widely used spatial light modulator at present, is actually a reflective spatial light modulator consisting of millions of individually programmable micromirrors. One micromirror represents one pixel, and a rotating device acting like a hinge is arranged below the micromirror to enable each micromirror unit to rapidly rotate under the control of digital signals so as to modulate incident light. DMD has two stable states: the 'ON' and 'off' states are defined when the micro-reflector rotates to +12 degrees, and at the moment, the reflected light is parallel to the optical axis of the projection lens and is imaged ON the display device through the projection lens; when the micro-reflector rotates to-12 degrees, namely an OFF state, the reflected light and the projection lens form an included angle at the moment, and the reflected light does not enter the projection lens and is absorbed by the stray light absorption device. The retention time of the "on" and "off" states of each micromirror cell is determined by the logic value of the bottom dual CMOS memory cell. The state holding time of the DMD micromirror unit can be controlled by adopting a binary PMW (pulse width modulation) subfield driving control method, and the longer the display time is, the stronger the stimulation to human eyes is, and the higher the formed gray scale level is. The effect of modulating the image grey scale can also be achieved by inputting a computer generated binary mask to the DMD. TIR is short for Total Internal Reflection. The TIR prism 21 functions to separate incident light obliquely incident ON the DMD micromirror unit from the ON-state light beam reflected by the DMD micromirror unit. Because the incident angles of the two beams of light reaching the total reflection surface are different, the incident angle of the two beams of light is greater than the critical angle to be totally reflected, and the incident angle of the two beams of light is less than the critical angle to be directly transmitted, the two beams of light are separated by utilizing the principle of total reflection.

Referring to fig. 3 again, in an embodiment, the waveguide display device further includes a computer, a third lens 51, a fourth lens 52 and a CCD camera 53, the fourth lens 52 is located between the optical modulator 22 and the CCD camera 53, the third lens 51, the optical modulator 22, the fourth lens 52 and the CCD camera 53 form an optical path connection in sequence, and the CCD camera 53 and the optical modulator 22 are electrically connected to the computer respectively. The third lens 51 is an achromatic imaging objective lens, and can image the light source image reflected by the object to be measured on the micromirror array surface of the optical modulation device 22; the fourth lens 52 is a variable power lens with adjustable magnification, which realizes the matching between the CCD camera 53 and the optical modulation device 22, and converges the image of the object to be measured on the light-sensing surface of the CCD camera 53 from the array surface of the optical modulation device 22, thereby completing the imaging of the dimming system. According to the energy loss of the light beam caused by the output coupling element 33, the computer generates a mask image capable of compensating the energy loss, the optical modulation device 22 adjusts the state of the micromirror according to the mask signal, and meanwhile, the optical modulation device 22 can adjust the state of the micromirror again according to whether the image acquired by the CCD camera 53 meets the requirement. The third lens 51 is a lens formed by bonding two optical components of a positive low refractive index and a negative high refractive index, and may be a doublet (two-element) or a triplet (three-element), but is not a single-piece glass lens. The optical axis of the third lens 51 makes an angle of about +24 ° with the normal of the micromirror array surface of the optical modulation device 22 according to the deflection characteristics of the DMD micromirror array. Similarly, the fourth lens 52 is not a single glass lens, but is a lens system composed of several lenses, and the optical axis of the system coincides with the optical axis of the camera and the normal line of the array surface of the optical modulation device 22. In fig. 3, the third lens 51 and the fourth lens 52 are each drawn in the form of a single convex lens for simplifying the optical path diagram.

Based on the combination of the above embodiments, in particular, please refer to fig. 2 again, which takes the stacking of three slab waveguides 22 as an example. The image light source from the image source 11 is reshaped and shimmed after passing through a first lens 12 and a lens 13, the first lens 12 not being shown in fig. 2. Then, the three color lights are reflected by the TIR prism 21 and enter the optical modulation device 22, and the brightness of the three color lights is non-uniformly modulated according to the respective energy loss in the slab waveguide 22, and finally, the three color lights are mixed into a color image with uniform brightness. The wavelengths of the light of the three colors red, green and blue are different, and the grating of the input coupling element 32 and the grating of the output coupling element 33 are difficult to control to respond to only one wavelength and not respond to other wavelengths at all, so that the dispersion phenomenon occurs. Therefore, for an augmented reality waveguide device implementing a color display function, two or three slab waveguides 22 are required to be stacked, one for each wavelength of each slab waveguide 22, in order to eliminate color crosstalk.

If the problem of uneven output is solved through the grating, grating parameters such as period, height, aspect ratio and the like need to be regulated, but the process manufacturing difficulty is high, and the whole system belongs to a back-end solution. In the embodiment, the projection unit is added between the incident light and the grating, and the DLP technology is utilized to enable the light beam to be modulated before entering the grating, so that the energy loss in the light beam transmission process is not required to be compensated through the grating, and the difficulty in the grating manufacturing process is solved.

Further, in an embodiment, the coupling unit 3 includes a slab waveguide 31, and an input coupling element 32 and an output coupling element 33 provided on the slab waveguide 31, and the illumination unit 1, the DLP projection unit 2, the input coupling element 32, and the output coupling element 33 are sequentially butted. The slab waveguide 31 is used for total reflection, transmitting an image light source. After the image light source modulated by the DLP projection unit 2 is diffracted by the input coupling element 32, the image light source diffracted in the first order satisfies the total reflection condition of the slab waveguide 31, in the process of being transmitted to the output coupling element 33, part of the light beam is diffracted out of the slab waveguide 31 and enters the human eye 4, and part of the light beam continues to be transmitted forward by total reflection until the energy of the light beam is consumed, so that the pupil expansion is realized in the process.

Further, in one embodiment, the input coupling element 32 is one of a binary rectangular grating, a tilted grating, and a blazed grating;

the output coupling element 33 is a two-dimensional grating, in order to expand the exit pupil in two directions; the included angle theta between two periods of the two-dimensional grating is 60 degrees, and other angles can be selected according to requirements. The specific parameters of the input coupling element 32 and the output coupling element 33 can be designed according to practical requirements.

And respectively carrying out groove depth modulation or duty ratio modulation or inclination angle modulation on the binary rectangular grating, the inclined grating, the blazed grating and the two-dimensional grating.

Further, in an embodiment, the two-dimensional grating is cylindrical or rectangular or hexagonal.

Further, in an embodiment, a gradual change film is disposed on the slab waveguide 31, so as to achieve a gradual change display effect.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.

Claims

1. A waveguide display device, comprising:

an illumination unit for providing a light source image;

2. A waveguide display device as claimed in claim 1, wherein the illumination unit comprises an image source, a first lens and a second lens, interfaced in sequence, the second lens interfaced with a DLP projection unit.

3. The waveguide display device according to claim 2, wherein the image sources comprise at least two colors, and each color image source is respectively provided with one DLP projection unit and one coupling unit.

4. A waveguide display device as claimed in claim 3, wherein the image source comprises three colours red, green and blue.

5. A waveguide display device as claimed in claim 1 wherein the DLP projection unit comprises a TIR prism and an optical modulation device, the illumination unit, TIR prism, optical modulation device and coupling unit being sequentially interfaced.

6. The waveguide display device according to claim 5, further comprising a computer, a third lens, a fourth lens and a CCD camera, wherein the fourth lens is located between the optical modulator and the CCD camera, the third lens, the optical modulator, the fourth lens and the CCD camera sequentially form an optical path connection, and the CCD camera and the optical modulation device are electrically connected with the computer respectively.

7. A waveguide display device as claimed in any one of claims 1 to 6, wherein the coupling unit comprises a slab waveguide and an input coupling element and an output coupling element provided on the slab waveguide, the illumination unit, the DLP projection unit, the input coupling element and the output coupling element being sequentially interfaced.

8. The waveguide display device of claim 7, wherein the input coupling element is one of a binary rectangular grating, a slanted grating, a blazed grating;

the output coupling element is a two-dimensional grating.

9. A waveguide display device according to claim 8, wherein the two-dimensional grating is cylindrical or rectangular or hexagonal.