CN105759431A - Three-dimensional light field displaying system - Google Patents

Abstract

The invention discloses a three-dimensional light field displaying system which comprises a display, a lens array, and a holographic function screen. The display is used for displaying a preset disparity sub image array. The lens array is used for projecting the preset disparity sub image array to the holographic function screen. The holographic function screen is used for providing a light field with a full parallax three-dimensional effect, wherein the lens in the lens array has a lens with an eccentric pupil. The lens array satisfies the following condition that the flare angle of the center of the disparity sub image in an ith row and an jth column of the preset disparity sub image array relative to the light through round hole of the lens Lij of the corresponding position in the lens array is U, I is an integer which is not larger than the row number of the disparity sub image array, and j is an integer which is not larger than the column number of the disparity sub image array.

Description

Three-dimensional light field display system

Technical Field

The invention relates to the technical field of display, in particular to a three-dimensional light field display system based on a spherical substrate eccentric pupil Fresnel lens array.

Background

The conventional display mode based on slit grating and lenticular lens grating cannot provide a continuous and smooth parallax due to the viewpoint limitation, and the display mode based on high-density viewpoint can only provide a continuous and smooth parallax within a smaller viewing angle range.

The multi-projection light field display mode solves the problem, and is a display mode capable of reconstructing a light field of a target object based on pixels, and the display method can provide continuous and smooth parallax in a larger viewing angle range. However, this display requires a relatively complex apparatus and takes up a relatively large amount of space.

The above problems are solved by the proposed light field display mode based on Liquid Crystal Display (LCD), in which each parallax sub-image displayed on the LCD and its corresponding imaging lens constitute a unit similar to a projector, and the problem of image blur due to the aberration of the imaging lens is reduced by reducing the clear aperture of the imaging lens.

The problems of the existing LCD-based light field display mode are as follows: since the clear aperture (i.e. the aperture of the clear circular hole) of the imaging lens is reduced, as shown in fig. 1, for the parallax sub-image at the edge of the LCD (e.g. the leftmost parallax sub-image in fig. 1), the center of the parallax sub-image is offset from the center of its corresponding imaging lens by a distance d₁The clear aperture of the imaging lens is D, D satisfies that S is N × D, N is the row number of the parallax sub-image array, S is the distance between adjacent parallax sub-images in the same row in the parallax sub-image array, D in FIG. 1₁The distance between the LCD and the lens array is equal to the opening angle of the center of the leftmost parallax sub-image relative to the light-passing circular hole of the leftmost lens in the lens array, and the opening angle is U₂The opening angle of the center of the middle parallax subgraph relative to the light-passing circular hole of the lens in the middle of the lens array is U₁，U₁And U₂Satisfies the following formula:

$U_1=\arctan \frac{D}{2D_1},U_2=\frac{1}{2}[\arctan \left(\frac{d_1+\frac{D}{2}}{D_1}\right)-\arctan \left(\frac{d_1-\frac{D}{2}}{D_1}\right)].$

the illumination of the center of the image plane (namely the center of the holographic functional screen) meets the following conditions:

$\begin{array}{c}{E}_1=\frac{\mathrm{k\πL}{\sin }^2{U}_1}{{\mathrm{\β}}^2}\\ E_2=\frac{\mathrm{k\πL}{\sin }^2{U}_2}{{\mathrm{\β}}^2}\end{array},$

wherein E is₁Image plane central illumination, E, of the intermediate parallax sub-image₂The image plane central illumination of the leftmost parallax sub-image, k is the absorption coefficient, β is the magnification factor, and L is the brightness of the LCD.

It can be seen that due to U₂＜U₁Therefore E is₂Less than E₁The illuminance on the image plane is reduced.

Disclosure of Invention

The invention aims to solve the technical problem that in the existing LCD-based light field display mode, because the clear aperture of an imaging lens is reduced, for parallax subgraphs at the edge part of an LCD, the centers of the parallax subgraphs and the centers of the corresponding imaging lenses are offset by a certain distance, so that the illumination on an image plane is greatly reduced.

To this end, in a first aspect, the present invention provides a three-dimensional light field display system, the system comprising: the display, the lens array and the holographic functional screen;

the display is used for displaying a preset parallax sub-image array;

the lens array is used for projecting the preset parallax sub-image array to the holographic functional screen;

the holographic functional screen is used for providing a light field with a full parallax three-dimensional effect;

wherein the lenses in the lens array are lenses with eccentric pupils, and the lens array satisfies the following conditions:

the center of the parallax sub-image in the ith row and the jth column in the preset parallax sub-image array is opposite to the lens L at the corresponding position in the lens array_ijThe opening angle of the light-passing round hole is U, i is a positive integer not larger than the number of rows of the parallax sub-image array, and j is a positive integer not larger than the number of columns of the parallax sub-image array.

Optionally, the display is a liquid crystal display LCD, and the lenses in the lens array are fresnel lenses.

Optionally, the number of lenses in the lens array is determined by the number of parallax sub-images in the preset parallax sub-image array.

Optionally, the number of parallax sub-images in the preset parallax sub-image array is N × N, where N is a positive integer, and the number of lenses in the lens array is also N × N.

Optionally, the lenses in the lens array are of an opaque square structure, and a light-passing circular hole is formed in the center of the square structure.

Optionally, the opening angle satisfies:

$U=\arctan \frac{D}{2D_1};$

wherein D is the aperture of the light-passing circular hole, D₁Is the distance between the display and the lens array.

Optionally, the light-passing circular hole of the lens with the eccentric pupil is obtained by cutting a circular area on a preset lens, and the center of the circular area satisfies:

$x_1=\frac{D_1}{D_1+D_2}X;$

$y_1=\frac{D_1}{D_1+D_2}Y;$

wherein x is₁Is the horizontal distance, y, of the center of the circular area from the center of the preset lens₁Is the vertical distance of the center of the circular area from the center of the preset lens, D₂And the distance between the lens array and the holographic function screen is defined as X, the horizontal distance between the center of the parallax sub-image and the center of the holographic function screen is defined as Y, the vertical distance between the center of the parallax sub-image and the center of the holographic function screen is defined as Y, and the parallax sub-image is a parallax sub-image corresponding to the position of the lens with the eccentric pupil in the preset parallax sub-image array.

Optionally, the lenses in the lens array are manufactured with a curvature C_sOn a spherical substrate, and a phase function of the lensSatisfies the following conditions:

wherein G is an aspherical coefficient,phi is the focal power of the lens, and lambda is the wavelength of the light wave; said C is_sThe value of G is determined by:

according to the preset aberration balance rule, C is adjusted_sAnd G, such that a diffuse spot radius is minimized, wherein the diffuse spot radius is determined by an eccentric aberration of the lens with an eccentric pupil.

Compared with the prior art, the three-dimensional light field display system provided by the invention has the advantages that the lens array is manufactured to meet the following requirements: the opening angle of the center of the parallax sub-image in the parallax sub-image array relative to the light-passing circular hole of the lens at the corresponding position in the lens array is U, and the lens is made into the lens with the eccentric pupil, so that the problems in the prior art are solved, and the three-dimensional light field display with better effect is realized.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.

FIG. 1 shows a block diagram of a light field display system based on a liquid crystal display LCD;

FIG. 2 illustrates a three-dimensional light field display system of the present invention;

FIG. 3 illustrates a three-dimensional light field display system of the present invention;

fig. 4 shows a schematic diagram of the acquisition of the clear circular aperture of the lens with eccentric pupil of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments, but not all embodiments, of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As shown in fig. 2, the present embodiment discloses a three-dimensional light field display system, which includes: the display can be a Liquid Crystal Display (LCD), and the lens in the lens array can be a Fresnel lens.

The display is used for displaying a preset parallax sub-image array; the number of parallax sub-images in the parallax sub-image array is a predetermined value, and different parallax sub-images display images of an object in different directions; the number of lenses in the lens array is determined by the number of parallax sub-images in the preset parallax sub-image array, as shown in fig. 3, the number of parallax sub-images in the parallax sub-image array is 81, that is, the parallax sub-image array is 9 rows and 9 columns, and the number of lenses in the lens array is also 81.

The lens array is used for projecting a preset parallax sub-image array to the holographic function screen;

the holographic functional screen is used for providing a light field with a full parallax three-dimensional effect;

wherein, the lens in the lens array is a lens with an eccentric pupil, and the lens array satisfies the following conditions: the center of the parallax sub-image in the ith row and the jth column in the preset parallax sub-image array is opposite to the lens L at the corresponding position in the lens array_ijThe opening angle of the light-passing round hole is U, i is a positive integer not larger than the number of rows of the parallax sub-image array, and j is a positive integer not larger than the number of columns of the parallax sub-image array. The opening angle U satisfies:

$U=\arctan \frac{D}{2D_1};$

wherein D is the aperture of the light-passing circular hole, D₁Is the distance between the display and the lens array.

As can be seen, in this embodiment, the opening angle U of the center of the leftmost parallax sub-image with respect to the light-passing circular hole of the leftmost lens in the lens array is₂The opening angle of the center of the middle parallax sub-image relative to the light passing round hole of the lens in the middle of the lens array is U₁It is known that the lens array with the eccentric pupil ensures that the edge parallax sub-image (i.e. the leftmost parallax sub-image) does not deviate too much from the center of the lens to cause too low image plane illumination, and meanwhile, the lens array with the eccentric pupil also ensures uniformity of illumination of the final reconstructed object image.

In a specific application, as shown in fig. 4, the light-passing circular hole of the lens with the eccentric pupil is obtained by cutting a circular area on a preset lens, and the center of the circular area satisfies:

$x_1=\frac{D_1}{D_1+D_2}X;$

$y_1=\frac{D_1}{D_1+D_2}Y;$

wherein x is₁Is the horizontal distance, y, of the center of the circular area from the center of the preset lens₁Is the vertical distance of the center of the circular area from the center of the preset lens, D₂The distance between the lens array and the holographic function screen is X, the horizontal distance between the center of the parallax sub-image and the center of the holographic function screen is Y, the vertical distance between the center of the parallax sub-image and the center of the holographic function screen is Y, and the parallax sub-image is a parallax sub-image corresponding to the position of a lens with an eccentric pupil in a preset parallax sub-image array.

Since the lens with eccentric pupil can introduce eccentric aberration, in order to reduce the influence of the eccentric aberration, in the embodiment, the lenses in the lens array are made with curvature C_sOn a spherical substrate, and a phase function of the lensSatisfies the following conditions:

wherein G is an aspherical coefficient,phi is the focal power of the lens, and lambda is the wavelength of the light wave; said C is_sThe value of G is determined by:

according to the preset aberration balance rule, C is adjusted_sAnd G, minimizing a diffuse spot radius, wherein the diffuse spot radius is determined by an eccentric aberration of a lens having an eccentric pupil.

In the present embodiment, it is preferred that,the lens with an eccentric pupil has four kinds of eccentric aberrations:

$S_1^{*}=S_1$

$S_2^{*}=S_2-4x_1{S}_1$

$S_3^{*}=S_3-2x_1{S}_2+x_1^2{S}_2$

$S_4^{*}=S_4$

$S_1=\frac{h^4{\mathrm{\φ}}^3}{4}[{\left(\frac{n}{n-1}\right)}^2+\frac{n+2}{n}{B}^2+\frac{4(n+1)}{n}B+\frac{3n+2}{n}{T}^2]-8\mathrm{\λ}{h}^{4}G$

$S_2=-\frac{h^2{\mathrm{\φ}}^{2}J}{2}[\frac{(n+1)}{n}B+\frac{2n+1}{n}T]$

S₃＝J²φ

$S_4=\frac{J^2\mathrm{\φ}}{n}$

$T=\frac{u+u^{\′}}{u-u^{\′}},A=\frac{\mathrm{\φ}}{2\mathrm{\λ}},B=\frac{2C_S}{\mathrm{\φ}}$

wherein,u, u' are first paraxial ray angles,h is the height of the intersection of the first paraxial ray and the lens, n is the refractive index of the lens, and J is the Lagrangian constant.

The technical terms referred to herein are as follows:

illuminance: the lux is a light flux per unit area of the surface of the subject.

Aberration: in an actual optical system, the results obtained by non-paraxial ray tracing and the results obtained by paraxial ray tracing do not coincide, and these deviations from the ideal state of gaussian optics (first order approximation theory or paraxial rays) are called aberrations.

Eccentric pupil: a partial pupil plane offset from the center of the entrance pupil.

Eccentric aberration: aberrations introduced by the eccentric pupil.

Clear aperture: refers to the effective aperture of the lens.

Spherical substrate: refers to a spherical substrate with a certain curvature, and the base of the traditional Fresnel lens is a plane.

Parallax: refers to the difference in the images of the object taken from different directions.

A parallax sub-graph: refers to images of an object taken in different directions.

A holographic functional screen: the optical screen with point diffusion function is made by holographic method.

Scattering angle: the scattering angle of the point spread of the holographic functional screen.

Viewpoint: an image taken from one direction of the real object.

Resolution ratio: refers to the number of pixels contained within an inch.

Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations fall within the scope defined by the appended claims.

Claims (8)

1. A three-dimensional light field display system, the system comprising:

the display, the lens array and the holographic functional screen;

the display is used for displaying a preset parallax sub-image array;

the lens array is used for projecting the preset parallax sub-image array to the holographic functional screen;

the holographic functional screen is used for providing a light field with a full parallax three-dimensional effect;

wherein the lenses in the lens array are lenses with eccentric pupils, and the lens array satisfies the following conditions:

the center of the parallax sub-image in the ith row and the jth column in the preset parallax sub-image array is opposite to the lens L at the corresponding position in the lens array_ijThe opening angle of the light-passing round hole is U, i is a positive integer not larger than the number of rows of the parallax sub-image array, and j is a positive integer not larger than the number of columns of the parallax sub-image array.

2. The display system of claim 1, wherein the display is a Liquid Crystal Display (LCD) and the lenses in the array of lenses are Fresnel lenses.

3. The display system of claim 1, wherein the number of lenses in the lens array is determined by the number of parallax sub-images in the predetermined parallax sub-image array.

4. The display system of claim 3, wherein the number of parallax sub-images in the predetermined parallax sub-image array is N × N, where N is a positive integer, and the number of lenses in the lens array is also N × N.

5. The display system of claim 3, wherein the lenses of the lens array are opaque square structures, and a light-passing circular hole is formed in the center of the square structures.

6. The display system of claim 5, the opening angle satisfying:

$U=\arctan \frac{D}{2D_1};$

wherein D is the same asAperture of the light circular hole, D₁Is the distance between the display and the lens array.

7. The display system according to claim 6, wherein the light-passing circular hole of the lens with the eccentric pupil is obtained by cutting a circular area on a preset lens, and the center of the circular area satisfies:

$x_1=\frac{D_1}{D_1+D_2}X;$

$y_1=\frac{D_1}{D_1+D_2}Y;$

wherein x is₁Is the horizontal distance, y, of the center of the circular area from the center of the preset lens₁Is the vertical distance of the center of the circular area from the center of the preset lens, D₂And the distance between the lens array and the holographic function screen is defined as X, the horizontal distance between the center of the parallax sub-image and the center of the holographic function screen is defined as Y, the vertical distance between the center of the parallax sub-image and the center of the holographic function screen is defined as Y, and the parallax sub-image is a parallax sub-image corresponding to the position of the lens with the eccentric pupil in the preset parallax sub-image array.

8. The method of claim 7A display system wherein the lenses of said lens array are fabricated with a curvature C_sOn a spherical substrate, and a phase function of the lensSatisfies the following conditions:

wherein G is an aspherical coefficient,phi is the focal power of the lens, and lambda is the wavelength of the light wave; said C is_sThe value of G is determined by:

according to the preset aberration balance rule, C is adjusted_sAnd G, such that a diffuse spot radius is minimized, wherein the diffuse spot radius is determined by an eccentric aberration of the lens with an eccentric pupil.