METHOD OF FORMING A FILM WITH A LENTICULAR LENS ARRAY
According to one aspect of the invention, there is provided a method of forming a film with a lenticular lens array, the method comprising providing a substrate; providing a mold having a plurality of nano-scale to micro-scale cavities that form the lenticular lens array on the substrate; having the mold contact the substrate; and forming the lenticular lens array by allowing portions of the substrate to partially fill the plurality of cavities.
The present invention relates to visual display technology. In particular, it relates to the design of a lens array for adapting a visual display device for spectacles-free three-dimensional viewing.
BACKGROUNDCurrent spectacles-free three-dimensional (3D) display technology using an optical element on a plastic film on top of a mobile devices' display typically utilizes one of two types of optical element technologies: parallax barrier technology or lenticular lens array technology. Lenticular lens array technology has an advantage over parallax barrier technology in terms of higher light transmitivity.
Yet, currently available 3D films utilizing lenticular lens array technology exhibit visible surface roughness on the film. This roughness translates to poor quality display images having coarse granularity and lacking sharp contours when the film is used while the display is operating in a two-dimensional (2D) mode. When operating in 3D mode, the visible roughness on the film creates artifacts that are perceptible to a viewer such as blended images (crosstalk) causing noticeable transitions between viewing zones and moiré-like artifacts. The cause of this roughness is due to two factors: a large lens width and a surface roughness of the fabricated lens. A width of typical lenticular lenses in existing 3D film is large, with dimensions in the micron-size range around 300 82 m to 600 μm. This size is due to limitations in tooling accuracy of existing fabrication means, such as conventional milling techniques. The roughness on the surface profile of the fabricated lens is also due to the inherencies of current tooling techniques, such as machine milling and laser writing, which generates a high degree of surface roughness.
An alternative method of fabricating lenticular lens arrays resulting in low dimension, smooth lenticular lenses uses a thermal resist reflow method. In this method, conventional photolithography (which is known to be able to achieve feature widths down to the optical diffraction limit (approximately 250 nm)) is first carried out to fabricate grating resist structures onto substrates. Then, through a controlled thermal resist reflow process, lenticular lens arrays can be formed as the melted polymer of the grating structure is reshaped into a reduced surface area lenticular profile structure. At the same time, the reflow process helps smoothen out any surface roughness of the lenticular lens profile.
Unfortunately, there is a limitation of the above-mentioned resist reflow method in the fabrication of the lenticular lens. There is a minimum aspect ratio (height(H)/width(W)) of approximately 1/23, or 0.04, below which the reflowed lens profile becomes deformed in the middle when using this method (from Nussbaum P, Volke R, Herzig H P, Eisner M and Haselbeck S 1997 Pure and Applied Optics 6 617). This limitation in the minimum aspect ratio of the lens results in a shortened focal length of the lens, following fabrication by a conventional thermal resist reflow process, thereby causing a blurry, non-sharp image due to misalignment of the focus plane with the image source.
With this limitation, the lenticular lens array fabricated onto the 3D film is unable to achieve clear 3D imaging due to the lenticular lens array being an out of focus plane of the LCD image source. An optimal focal length is required by the lenticular lens array in order to achieve good 3D imaging.
Thus, what is needed is a lenticular lens array 3D film with a low width dimension (preferably lower than the current 300 μm width resolution of existing film fabrication technologies) and with an ultrasmooth surface to enable visualization of good quality display images in a display's 2D mode and 3D mode, as well as a low aspect ratio lenticular lens structure to allow sufficient focal length to focus the image with its paired image source.
SUMMARYThe present invention overcomes the problems in existing 3D film rough film surfaces and overcomes the limitation of existing thermal resist reflow methods that can only achieve a minimum aspect ratio lenticular lens structure of approximately 0.04.
In order to provide smooth film surface lenticular lens arrays, the present invention employs by design a small width dimension lenticular structure having less than a 300 μm lens width and employs photolithography and thermal resist reflow techniques to achieve a lenticular lens structure having a small lens width dimension with an ultrasmooth surface profile.
In order to achieve a reduced minimum aspect ratio lenticular lens structure, the present invention uses a variation of thermal nanoimprinting by partial filling (described in further detail below with respect to
According to one aspect of the invention, there is provided a method of forming a film with a lenticular lens array, the method comprising providing a substrate; providing a mold having a plurality of nano-scale to micro-scale cavities that form the lenticular lens array on the substrate; having the mold contact the substrate; and forming the lenticular lens array by allowing portions of the substrate to partially fill the plurality of cavities.
Example embodiments of the invention will be better understood and readily apparent to one of ordinary skill in the art from the following written description, by way of example only, and in conjunction with the drawings. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention, in which:
The following provides sample, but not exhaustive, definitions for expressions used throughout various embodiments of the invention disclosed herein.
The term “film” may mean a thin layer which modulates light that transmits through due to the presence of optical elements present within the thin layer.
The phrase “lenticular lens array” may mean a plurality of lenses arranged in a specific pattern, the lenses and their specific arrangement designed so that when viewed from slightly different angles, different images can be seen. Images seen through the lenticular lens array are given an illusion of depth, or appear to change or move as the images are viewed from different angles.
The word “substrate” may mean a structure, fabricated from any transparent material such as plastic, polymethylmethacrylate, polycarbonate and polyethylene, or glass, serving as a base for the lenticular lens array.
The phrase “cavities” may mean a pattern formed on a mold surface that is used to facilitate the formation of the lenticular lens array on the substrate. Each of the cavities may be a depression providing a hole on the mold surface within which a lens of the lenticular lens array will be formed. The cavities are also sized to accommodate formation of lenses with nanometer to micrometer sized widths, such as between 50 nm to 300 μm, the lenses further having an aspect ratio of less than or equal to 0.04.
The term “aspect ratio” may mean the ratio of the height and width of each lens.
The phrase “portions of the substrate” refer to parts of the substrate that are surrounded by the micro-scale cavities of the mold when the mold is in contact with the substrate.
The phrase “partially fill” may mean that each lens of the lenticular lens array is formed within the space provided by each of the plurality of cavities, so that each lens does not come into contact with the side wall of the respective cavity and this space is not completed filled.
DETAILED DESCRIPTIONIn the following description, various embodiments of the invention are described with reference to the drawings, where like reference characters, generally refer to the same parts throughout the different views.
Referring to
A side planar view of a typical implementation of a film 204 with an array of lenticular lens 200 paired with an image source 206 seen through a glass/plastic screen 208 of a mobile device 210 is shown in
In accordance with a present embodiment of the invention, a lenticular array structure is fabricated on a film and used for three-dimensional viewing of visual displays. The present embodiment of the invention achieves a symmetric profile and reduced minimum aspect ratio through a variation of conventional thermal nanoimprinting, the variation being partially filling cavities of a mold that is fabricated. The mold allows fabrication of a 3D film having a lenticular lens array for performing spectacles-free 3D viewing. The unique lenticular lens array structure includes a small lens width dimension structure as well as an ultrasmooth surface and low aspect ratio (<0.04) lenticular lens structure fabricated onto a plastic substrate (e.g. a polycarbonate (PC) film). The resulting 3D film allows users to clearly view 3D images without compromising the quality of existing 2D display images when the 3D film is used on the display in 2D mode.
In step 302, a substrate is provided. In step 304, a mold is provided, having a plurality of nano-scale to micro-scale cavities that form the lenticular lens array on the substrate. In step 306, contact of the mold with the substrate is made. In step 308, the lenticular lens array is formed by allowing portions of the substrate to partially fill the plurality of cavities.
The dimension of the mold cavities is determined by optical diffraction limit. A dimension of 250 nm is achievable using UV photolithography. If higher resolution lithography, e.g. e-beam lithography, is employed, the dimension of the mold cavities can be reduced from 250 nm to around 50 nm.
Step 308 may be performed using a mechanical process, such as thermal nanoimprinting. However, the thermal nanoimprinting used in step 308 varies from a conventional thermal nanoimprinting process as follows. In a conventional thermal nanoimprint process (not shown), a substrate material is brought at above its glass transition temperature that causes the substrate to be in low viscosity and completely fill up the cavities of the mold. On the other hand, in the embodiment shown in
Referring to
Each lens 318 of the lenticular lens array has a symmetric cross-sectional profile. Each lens 318 is generally symmetric about a longitudinal axis extending along a centre and intersecting a base of the respective lens.
In addition, referring to
Thus, fabrication of a lenticular lens array using the method described with respect to
Referring to
Referring to
Referring to
Referring to
Using the process shown in
UV photolithography. If higher resolution lithography, e.g. e-beam lithography (not shown), is employed, the dimension of the mold cavities can be reduced from 250 nm to around 50 nm.
As can be seen, processing in accordance with the embodiment described with respect to
Referring to
Microscopic imaging of the films also shows the smoother surface of the film fabricated in accordance with the embodiment described with respect to
From
It will be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in the embodiments without departing from a spirit or scope of the invention as broadly described. The embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive.
Claims
1. A method of forming a film with a lenticular lens array, the method comprising:
- providing a substrate;
- providing a mold having a plurality of nano-scale to micro-scale cavities that form the lenticular lens array on the substrate;
- having the mold contact the substrate; and
- forming the lenticular lens array by allowing portions of the substrate to partially fill the plurality of cavities.
2. The method of claim 1, wherein an aspect ratio of each lens of the lenticular lens array is adjusted by controlling an extent to which the portions of the substrate partially fill the plurality of cavities.
3. The method of claim 2, further comprising varying a duration over which the lenticular lens array is formed to control the extent to which the portions of the substrate partially fill the plurality of cavities.
4. The method of claim 2, wherein the aspect ratio of each lens is less than or equal to 0.04.
5. The method of claim 1, wherein each lens of the lenticular lens array has a symmetric cross-sectional profile.
6. The method of claim 5, wherein each lens is generally symmetric about a longitudinal axis extending along a centre and intersecting a base of the respective lens.
7. The method of claim 1, wherein the formation of the lenticular lens array occurs at a range of around 10° below or above the glass transition temperature of the substrate.
8. The method of claim 7, wherein the formation of the lenticular lens array occurs at a pressure of around 10 Bar to 60 Bar.
9. The method of claim 1, wherein the mold comprises polydimethylsiloxane (PDMS).
10. A film fabricated from the method of claim 1, comprising a lenticular lens array, wherein each lens has a width of less than 300 μm.
11. The film of claim 10, wherein each lens has an aspect ratio of less than or equal to 0.04.
12. The film of claim 10, wherein each lens has a smooth surface.
13. The film of claim 10, wherein the lenticular lens array is provided on a substrate fabricated from flexible material.
14. The film of claim 13, wherein the substrate comprises any one or more of the following materials: plastic, polymethylmethacrylate, polycarbonate and polyethylene.
15. A display configured for two dimensional and three dimensional content, the display comprising a film of claim 10, the film for spectacles-free three dimensional viewing of the three dimensional content.
Type: Application
Filed: Nov 29, 2013
Publication Date: Nov 5, 2015
Inventors: Beng Soon Tan (Singapore), Chee Fatt Frank Chan (Singapore), Yun Xu (Singapore), Bee Khuan Jaslyn Law (Singapore), Yee Chong Loke (Singapore), Hong Yee Low (Singapore)
Application Number: 14/648,063