GB2550885A

GB2550885A - Method and apparatus for an enhanced-resolution light field display

Info

Publication number: GB2550885A
Application number: GB1609360.1A
Authority: GB
Inventors: Ma Xiaoqi; Tan Baolin; Lu Min; Kang Jianghui; Wu Yu; Han He Johnny
Original assignee: Shenzhen Yinglun Tech Ltd; Euro Electronics (uk) Ltd
Current assignee: Shenzhen Yinglun Tech Ltd; Euro Electronics (uk) Ltd
Priority date: 2016-05-26
Filing date: 2016-05-26
Publication date: 2017-12-06
Also published as: GB201609360D0

Abstract

An enhanced space resolution light field display 1 comprises a dynamic microlens array 2, a high refresh rate screen 3 and a signal processor 4. The dynamic microlens array 2 may have its focal lengths adjusted by changes in voltage across them to either change the radius or the refractive index of each lens. The refresh rate of the screen may determine the number of depth layers and the image quality generated by the signal processor 4. The display content may be divided up into several depth layers. The microlens array 2 may firstly change from using an initial value of focal length to an extreme value of the focal length, before changing from using the extreme value of the focal length back to the initial value. The signal processor 4 may display different depth layer scenes one after another according to the changes in focal length.

Description

Method and Apparatus for an Enhanced-Resolution Light Field Display

Background

This invention relates to an enhanced resolution light field (LF) display apparatus. More particularly this present invention relates to a dynamic microlens array, a high refresh rate screen and a signal processing system.

The technologies of three-dimensional (3D) imaging have been the most popular display methods in the recent 10 years. Compared with other technologies, LF displays can represent the real original 3D scene to a viewer and avoid the accommodation-vergence conflict. A LF display can be easily implemented by overlaying a microlens array on a display.

Although a LF display can display a real 3D scene, the low space resolution and narrow viewing angle limit its development and commercialization. Two important parameters of a LF display, the space resolution and the angular resolution, are limited by the size of a display screen and the size of display pixel. For one certain display screen, when the angular resolution is increased, the space resolution has to be reduced; in the same way, the space resolution is increased while the angular resolution has to be reduced. So there is a tradeoff between the angular resolution and the space resolution. One of the solutions on this problem is to increase the size of the display. But this increase isn’t unlimited, and cannot solve this problem radically.

This present invention gives a solution to enhance the space resolution of a LF display without reducing the angular resolution. Here, there are several problems to solve to get a high resolution LF display. The first problem is to adjust the focal length of a microlens array to the required data. The second problem is to prepare the certain elemental images for the certain spatial positions. The thirst problem is to arrange the play sequence.

Statements of invention

The present invention implements an enhanced space resolution LF display by the method that each display unit displays the different contents in different time intervals, and the dynamic microlens array projects these display contents (elemental images) to different spatial position. These different contents refresh quickly enough that these discrete images blend into a single image to a viewer. In this case, a small size display unit of this invention can display the image content which was displayed by a big display unit without the present invention. The small size display unit results in that more microlens lenslets will be used to restructure the original light field which means a higher space resolution. At the same time, the same image contents are projected to the space during a period which means the angular resolution in the invention isn’t reduced in comparison with the LF display without this invention.

To project the different image content to different spatial position in different time interval, a microlens array cannot be the traditional static lens, and should be adjusted in different time intervals. Here, the invention defines a microlens array having an adjustable focal length is a dynamic microlens array. As it well known, adjusting either the radius or the refractive index of a lens is a method to change its focal length. According to the thin lens imaging equation and optical geometry, the different display contents can be project to different spatial position in the case that the focal length is adjusted while the object distance doesn’t change. In the present invention, a microlens lenslet can cover an Μ x N array of display pixels. Here, M and N are the numbers of rows and columns, respectively. A display screen with high refresh rate is employed to satisfy the display requirement which is to display multiple groups of elemental images in a display period to bound these multiple images to a single image. It means that the refresh rate of a single group of elemental images should be faster than 60Hz in order to employ the human being’s persistence of vision to get a smooth image. This requirement results in that if there are four groups of elemental images for four time intervals, the refresh rate of the screen should be at least 240Hz.

In this present invention, the image preparation and processing system is a very important system. It prepares the different groups of elemental images for different time intervals, and delivers them to the display.

Detailed Description of the Invention

An example LF display of the present invention will now be described by referring to the accompanying figures in which:

Figure lisa schematic diagram of an enhanced space resolution LF display;

Figure 2 is a schematic diagram of the arrangement of the dynamic microlens lenslets and the corresponding pixels;

Figure 3 is the working flow of this LF display;

Figure 4 is a schematic diagram of an elemental image and its corresponding lenslet in two time intervals;

Figure 5 is a schematic diagram of a pixel on an elemental image and its image during a period.

This present invention will be described in detail in relation to a LF display 1 shown in Figure 1. In this embodiment, a LF display 1 is composed of a dynamic microlens array 2, a high refresh rate screen 3, and a signal processor 4. The dynamic microlens array 2 is composed of / x / array of lenslets 5, where / and J are the numbers of rows and columns, respectively. Its refractive index is adjustable with the change of the voltage, which leads to the adjustable focal length. The refresh rate of the screen 3 is 250Hz. Hence, there can be four different image contents to be bounded to restructure the original LF. The gap between the dynamic microlens array 2 and the screen 3 is g, here g > f f is the current focal length of the dynamic microlens array. A signal processor 4 provides the processed image signals to the display.

The dynamic microlens lenslets 5 are arranged as the hexagonal array which is shown in Figure 2. Each microlens lenslet 5 can cover 4x4 display pixels 6. Here, the diameter of a lenslet 5 is PL, the horizontal and vertical pitches of the dynamic microlens array 2 are PLx and PLy, respectively, and

The working flow of this LF display 1 in one period is shown in Figure 3. During one working period, this LF display 1 can restructure two 3D scenes, and each 3D scene is formed by four discrete scenes. Here, these discrete scenes are named as the sub light field. In this case, the working period can be divided into two parts. In each part, the refractive index of the lenslet 5 will be adjusted 3 times. As it well known,

Here, R is the radius of the lens, and n is the refractive index of the lens. During the first part, the refractive index controlled by the voltage will increase, which leads to a smaller focal length.

According to the thin lens imaging equations, there is

here l is the image distance.

When / is smaller, the image distance l will reduce as well. During the second part, the refractive index will return to the initial data, and the focal length / will increase to the initial value. Therefore, the image distance of each sub LF will increase as well. The signal processor 4 must prepare the corresponding image contents for the four time intervals in each part. In this embodiment, an original 3D scene will be divided into four layers which depend on their depth. In the first part, the front layer will be displayed in the first time interval, then the farther layers will be displayed in the second and third time intervals, finally the farthest layer will be displayed in the fourth time interval. During the second part, the display sequence is reversed. The farthest layer will be displayed at first in the fifth time interval, then the nearer layers are displayed in the sixth and seventh time intervals, at last the front layer is displayed in the eighth time intervals.

Figure 4 shows an elemental image display area and the adjustable microlens array 2 during the first two time intervals. In this case, a lenslet 5 can cover 4x4 pixels 6, which means PL = 4p, and the pitch of an elemental image Pei is Pei = 4p. Here, the pitch of a pixel 6 is p. The changes of the refractive index are hard to show in the figure, hence the changes of the refractive index are shown by the changes of the radius of the lenslet 6. It makes the figure easier to be understood. The lenslet 6 used the solid line to show is the lenslet 6 in the first time interval. The lenslet 6 in the second time interval is described by the dot line. At the same time, the image in first time interval is shown by the solid line, and the image is shown by the dot line in second time interval.

Claims

Claims 1 An enhanced space resolution light field display comprising a dynamic microlens array, a high refresh rate screen, and a signal processor. 2 An enhanced space resolution light field display as claimed in claim 1, wherein the microlens array has a dynamic focal length which can be adjusted by the voltage, the voltage can change either the radius of the lens or the refractive index. 3 An enhanced space resolution light field display as claimed in claim 1, wherein the screen has a high refresh rate which determines the number of the depth layers and the image quality, more layers need much higher refresh rate. 4 An enhanced space resolution light field display as claimed in claim 1, wherein the display content will be divided into several depth layer. 5 An enhanced space resolution light field display as claimed in claim 1, wherein the display period includes two parts, in the first part, the focal length of the microlens array changes from the initial value to the extreme value (the maximum focal length or the minimum focal length); in the second part, the focal length will change from the extreme value to the initial value. 6 The working period of an enhanced space resolution light field display as claimed in claim 5, wherein the different depth layer scenes are displayed one after another according to the changes of the focal length.