CN105759431B - A kind of 3 d light fields display system - Google Patents

Abstract

The invention discloses a three-dimensional light field display system. The system includes: a display, a lens array, and a holographic function screen; the display is used to display a preset parallax sub-image array; the lens array is used to display the preset The parallax sub-image array is projected onto the holographic functional screen; the holographic functional screen is used to provide a light field with a full parallax stereoscopic effect; wherein, the lens in the lens array is a lens with an off-center pupil, and the lens The array satisfies the following conditions: the opening angle of the center of the parallax sub-image located in the i-th row and the j-th column in the preset parallax sub-image array relative to the light-through circular hole of the lens L _ij at the corresponding position in the lens array is U, i is a positive integer not greater than the number of rows of the disparity sub-image array, and j is a positive integer not greater than the number of columns of the disparity sub-image array.

Description

A three-dimensional light field display system

technical field

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

Background technique

The traditional display method based on slit grating and cylindrical lens grating cannot provide a continuous and smooth parallax due to the limitation of viewpoint, and the display method based on high-density viewpoint can only provide continuous and smooth parallax in a small viewing angle range .

The multi-projection light field display method solves the above problems. It is a pixel-based display method that can reconstruct the light field of the target object. This display method can provide continuous and smooth parallax in a large viewing angle range. . However, the equipment required by this display method is relatively complicated and takes up a large space.

The proposed light field display method based on Liquid Crystal Display (LCD) solves the above problems. In this display method, each parallax sub-image displayed on the LCD and its corresponding imaging lens form a projector-like The unit reduces the problem of imaging blur caused by the aberration of the imaging lens by reducing the clear aperture of the imaging lens.

The problems existing in the existing LCD-based light field display methods are as follows: due to the reduction of the clear aperture of the imaging lens (that is, the aperture of the clear circular hole), as shown in FIG. 1), the center of the parallax subgraph has an offset distance d ₁ from the center of the corresponding imaging lens, the clear aperture of the imaging lens is D, and D satisfies: S=N×D, N is The number of rows of the parallax sub-image array, S is the spacing between adjacent parallax sub-images in the same row in the parallax sub-image array, D1 in Figure ₁ is the distance between the LCD and the lens array, and the center of the leftmost parallax sub-image is relative to the lens array The opening angle of the light-passing circular hole of the leftmost lens is U ₂ , and the opening angle of the center of the parallax sub-image relative to the light-passing circular hole of the lens in the middle of the lens array is U ₁ , and U ₁ and U ₂ satisfy The following formula:

The illuminance at the center of the image plane (that is, the center of the holographic function screen) satisfies:

Among them, E ₁ is the central illuminance of the image plane of the middle disparity sub-image, E ₂ is the illuminance of the image plane center of the leftmost disparity sub-image, k is the absorption coefficient, β is the magnification, and L is the brightness of the LCD.

It can be seen that since U ₂ < U ₁ , E ₂ is smaller than E ₁ , so the illuminance on the image plane is reduced.

Contents of the invention

The technical problem to be solved by the present invention is that in the existing LCD-based light field display mode, due to the reduction of the light aperture of the imaging lens, for the parallax sub-images at the edge of the LCD, the centers of these parallax sub-images have a certain distance from the center of the corresponding imaging lens. The distance shifts, so the illuminance on the image plane is reduced a lot.

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

The display is used for displaying a preset disparity sprite array;

The lens array is used to project the preset parallax sprite array onto the holographic functional screen;

The holographic functional screen is used to provide a light field with full parallax stereo effect;

Wherein, the lens in the lens array is a lens with an off-center pupil, and the lens array satisfies the following conditions:

The opening angle of the center of the parallax sub-image located in the i-th row and the j-th column in the preset parallax sub-image array relative to the light-through circular hole of the lens L _ij at the corresponding position in the lens array is U, and i is not A positive integer greater than the number of rows of the disparity submap array, and j is a positive integer not greater than the number of columns of the disparity submap 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 opaque square structures, and a light-through circular hole is opened in the center of the square structure.

Optionally, the opening angle satisfies:

Wherein, D is the aperture of the light _- through circular hole, and D1 is the distance between the display and the lens array.

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

Wherein, x1 is the horizontal distance between the center _of the circular area and the center of the preset lens, _y1 is the vertical distance between the center of the circular area and the center of the preset lens, and _D2 is the lens The distance between the array and the holographic functional screen, X is the horizontal distance between the center of the parallax sub-image and the center of the holographic functional screen, Y is the vertical distance between the center of the parallax sub-image and the center of the holographic functional screen, and the parallax sub-image is the preset The parallax submap corresponding to the position of the lens with an off-center pupil in the disparity submap array is provided.

Optionally, the lenses in the lens array are made on a spherical substrate whose curvature is C _s , and the phase function of the lens Satisfy:

Among them, G is the aspheric coefficient, φ is the focal power of the lens, and λ is the wavelength of the light wave; the values of C _s and G are determined in the following way:

According to a preset aberration balance rule, C _s and G are adjusted to minimize the radius of the blurred spot, wherein the radius of the blurred spot is determined by the decentering aberration of the lens with a decentered pupil.

Compared with the prior art, the three-dimensional light field display system of the present invention satisfies the following requirements by making the lens array: the opening angle of the center of the parallax sub-image in the parallax sub-image array relative to the light-through circular hole of the lens at the corresponding position in the lens array is U, and making the lens as a lens with an off-center pupil solves the problems existing in the prior art, and realizes a three-dimensional light field display with better effect.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1 shows the structural diagram of a light field display system based on a liquid crystal display LCD;

Fig. 2 shows a kind of three-dimensional light field display system of the present invention;

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

Fig. 4 shows a schematic diagram of obtaining a light-through circular hole of a lens with an off-center pupil according to the present invention.

Detailed ways

In order to make the purpose, 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 in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are the Some, but not all, embodiments are invented. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

As shown in Figure 2, this embodiment discloses a three-dimensional light field display system, the system includes: a display, a lens array, a holographic function screen, 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 to display 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 in different directions of objects; the number of lenses in the lens array is determined by The number of parallax sub-images in the preset parallax sub-image array is determined. As shown in FIG. The number of lenses in is also 81.

The lens array is used to project the preset parallax sprite array to the holographic functional screen;

The holographic functional screen is used to provide a light field with a full parallax stereoscopic 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 i-th row and j-th column in the preset parallax sub-image array is relative to the corresponding The opening angle of the light-through circular hole of the lens L _ij at the position is U, i is a positive integer not greater than the number of rows of the parallax sub-image array, and j is a positive integer not greater than the number of columns of the parallax sub-image array. Zhang Angle U satisfies:

Wherein, D is the aperture of the light _- through circular hole, and D1 is the distance between the display and the lens array.

It can be seen that in this embodiment, the center of the leftmost parallax subfigure is relative to the aperture angle U ₂ = U of the light-through circular hole of the leftmost lens in the lens array, and the center of the parallax subfigure in the middle is relative to the center of the lens array. The opening angle of the light-passing circular hole of the lens is U ₁ =U. From this, it can be known that the lens array with eccentric pupil ensures that the edge parallax sub-image (that is, the leftmost parallax sub-image) will not deviate from the center of the lens Too much leads to low illumination of the image plane. At the same time, the lens array with off-center pupils also ensures the uniformity of illumination of the final reconstructed object image.

In a specific application, as shown in Figure 4, the light-through circular hole of the lens with an off-center pupil is obtained by intercepting a circular area on the preset lens, and the center of the circular area satisfies:

Wherein, x1 is the horizontal distance between the center _of the circular area and the center of the preset lens, _y1 is the vertical distance between the center of the circular area and the center of the preset lens, and _D2 is the distance between the lens array and the preset lens. The distance of the holographic functional screen, X is the horizontal distance between the center of the parallax sub-image and the center of the holographic functional screen, Y is the vertical distance between the center of the parallax sub-image and the center of the holographic functional screen, and the parallax sub-image is a preset parallax sub-image Disparity submap in the map array corresponding to lens positions with decentered pupils.

Since a lens with a decentered pupil will introduce decentering aberrations, in order to reduce the influence of decentering aberrations, in this embodiment, the lenses in the lens array are fabricated on spherical substrates with a curvature of C _s , and the phase function of the lenses Satisfy:

Among them, G is the aspheric coefficient, φ is the focal power of the lens, and λ is the wavelength of the light wave; the values of C _s and G are determined in the following way:

According to the preset aberration balance rule, C _s and G are adjusted to minimize the radius of the blurred spot, where the radius of the blurred spot is determined by the decentering aberration of the lens with the decentered pupil.

In this embodiment, there are four types of decentering aberrations of the lens with decentered pupils:

S ₃ =J ² φ

in, u, u' are the first paraxial ray angle, 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 Lagrang daily quantity.

The technical terms involved in this article are as follows:

Illuminance: It is commonly referred to as Lux (lux), which means the luminous flux per unit area on the surface of the subject.

Aberration: In the actual optical system, the results obtained by non-paraxial ray tracing are inconsistent with the results obtained by paraxial ray tracing. These deviations from the ideal conditions of Gaussian optics (first-order approximation theory or paraxial ray) are called aberrations.

Eccentric Pupil: Part of the pupil surface that deviates from the center of the entrance pupil.

Eccentric Aberration: Aberration introduced by an off-center pupil.

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

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

Parallax: Refers to the difference in images of objects taken from different directions.

Disparity submap: Refers to images of objects acquired in different directions.

Holographic functional screen: an optical screen with point diffusion function made by holographic method.

Scattering angle: the scattering angle of the point diffusion of the holographic function screen.

Viewpoint: An image taken from one direction of the actual object.

Resolution: 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 can make various modifications and variations without departing from the spirit and scope of the present invention. within the bounds of the requirements.

Claims (4)

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 circular 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 number of the lenses in the lens array is determined by the number of the preset parallax sub-images in the parallax sub-image array, the lenses in the lens array are of an opaque square structure, and a light-passing round hole is formed in the center of the square structure;

the opening angle U satisfies:

<mrow> <mi>U</mi> <mo>=</mo> <mi>a</mi> <mi>r</mi> <mi>c</mi> <mi>t</mi> <mi>a</mi> <mi>n</mi> <mfrac> <mi>D</mi> <mrow> <mn>2</mn> <msub> <mi>D</mi> <mn>1</mn> </msub> </mrow> </mfrac> <mo>;</mo> </mrow>

wherein D is the aperture of the light-passing circular hole, D₁The distance between the display and the lens array;

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 the following conditions:

<mrow> <msub> <mi>x</mi> <mn>1</mn> </msub> <mo>=</mo> <mfrac> <msub> <mi>D</mi> <mn>1</mn> </msub> <mrow> <msub> <mi>D</mi> <mn>1</mn> </msub> <mo>+</mo> <msub> <mi>D</mi> <mn>2</mn> </msub> </mrow> </mfrac> <mi>X</mi> <mo>;</mo> </mrow>

<mrow> <msub> <mi>y</mi> <mn>1</mn> </msub> <mo>=</mo> <mfrac> <msub> <mi>D</mi> <mn>1</mn> </msub> <mrow> <msub> <mi>D</mi> <mn>1</mn> </msub> <mo>+</mo> <msub> <mi>D</mi> <mn>2</mn> </msub> </mrow> </mfrac> <mi>Y</mi> <mo>;</mo> </mrow>

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.

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 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.

4. The display system of claim 1, wherein the lenses of the 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.