WO2004098205A2

WO2004098205A2 - Lenticular panel with variable pitch

Info

Publication number: WO2004098205A2
Application number: PCT/IL2004/000352
Authority: WO
Inventors: Itzchak Bar-Yona
Original assignee: Lubartech Ltd.
Priority date: 2003-04-28
Filing date: 2004-04-26
Publication date: 2004-11-11
Also published as: WO2004098205A3

Abstract

The present invention is a method for generating a printed interlaced image and lenticular sheet or panel combination with a variable pitch (R1). The method of the invention results in the advantage of preventing unauthorized viewing or reproduction of the information contained in the interlaced image.

Description

LENTICULAR PANEL WITH VARIABLE PITCH

Field of the Invention

The present invention is related to the field of lenticular displays.

Specifically, the invention provides a method of guarantying the

relationship between the lenticular panel and the program used to print the

interlaced image. The method of the invention also provides a way to encode

printed documents.

BACKGROUND of the Invention

One of the commercial difficulties of the lenticular display industry is the

ease with which, using readily available and relatively inexpensive

materials and computer programs their products can be reproduced or, in the case of printed material comprising interlaced images, viewed without

the need for purchasing the original viewer.

It is a necessary goal of the industry to develop a relationship between the lenticular sheet and printing such that if this relationship were not satisfied the images could not be viewed. It is therefore a purpose of the present invention to provide a method that

creates a relationship between the lenticular sheet and interlaced image

that is virtually impossible to reproduce without precise knowledge of how it was created.

Further purposes and advantages of this invention will appear as the

description proceeds.

Summary of the Invention

The present invention provides a method for generating a printed interlaced

image and lenticular sheet or panel combination which comprises the steps

of:

a) creating a transparent lenticular sheet or panel comprising linear

lenses having a basic pitch; wherein, at least a portion of the sheet or

panel comprises a plurality of lenses having variable pitches resulting

in a given cumulative pitch;

b) processing said printed interlaced image in a way that the pitch of the

interlaced print is variable in accordance with the variable pitch of

the lenses on the lenticular sheet or panel.

The progressive variation between two adjacent lenses is less then 10% of the width of one of the lenses and the cumulative pitch distance of the sheet

or panel having variable lenses is different than the cumulative pitch distance of a hypothetical sheet, comprising uniform lenses having the same

basic pitch by a factor of at least half of the basic pitch. The difference

between the cumulative pitch of the lenticular sheet is different from the

cumulative pitch of the interlacing by an amount that exceeds the tolerance

of the basic pitch.

The variation of the pitch of the lenses and of the complementary interlaced

print can be random or correspond to a mathematical formula.

All the above and other characteristics and advantages of the invention will

be further understood through the following illustrative and non-limitative

description of preferred embodiments thereof, with reference to the

appended drawings.

Brief Description of the Drawings

- Fig. 1 schematically shows a lenticular sheet and defines parameters

involved in its description; and

- Fig. 2 is shown an example of a lenticular lens sheet according to the

invention.

Detailed Description of Preferred Embodiments

As is well known to experienced persons, in practice an interlaced image is

created digitally using digital cameras and computers guided by appropriate software and then stored in the computer's memory to be eventually printed

on a suitable substrate. In the description hereinbelow, the substrate will be

referred to as a sheet, but it is to be understood that by sheet is meant any

suitable substrate such as a film, sheet, or panel, made of any suitable

material, such as plastic or paper. The methods, hardware, and software

required for producing and printing interlaced images are well known in the

art and will not be discussed in detail hereinbelow for reasons of brevity.

However a brief description of one of the methods of creating an interlaced

image is useful as an introduction to the description of the present

invention.

The first step in creating an interlaced image is to record graphically or with

a digital camera several basic images and store them in the memory of a

computer. In the next step the sizes of the basic images are adjusted resulting in images having equal height H and width W. Each of the basic

images is then electronically cut into n equal strips, referred to as "lines".

Each of the resulting lines for each of the images has height H and width w,

where w = W/n. Following instructions provided by the software, the computer then merges the information contained in the basic images into a

single combined image (computer file) by arranging the strips of width w in

the order Al, Bl, etc.,A2, B2, etc...... to form a combined image having the same height H as each of the original images and width W times the number of basic images. Finally, the interlaced image is created by compressing the width of the

combined image uniformly to W, in order to retain the proper proportions in

the images that will be observed when looking at the interlaced image

through the lenticular sheet. Each line of the interlaced image has width w,

defined as the pitch, and contains one compressed line of the corresponding

line from each of the basic images. The interlaced image is stored as a file in a computer and is eventually printed on an indicia carrier using

conventional means.

In order to be able to view the basic images that have been interlaced and printed on the page, the interlaced image is viewed through a lenticular

array of lenses created on the top face of transparent sheet or panel. The

lenses have the same general configuration as the fines of printing,

generally an array of linear cylindrical lenses. If the requirements listed hereinbelow for a lenticular display are met, then the basic images are alternately displayed by changing the viewing angle of the interlaced image

through the lenses or by causing relative motion, in a controlled manner,

between the interlaced image and the lenses.

The fundamental requirements of a lenticular display are the following:

1. The pitch of the interlaced image must be essentially equal to the pitch

of the lenses. 2. The distance between the interlaced image and the lenses must be

constant and essentially equal to the focal length of the lenses.

3. For dynamic displays, exact alignment between the interlaced image and

the array of lenses must be established and maintained during relative motion of the lenses with respect to the printing.

These requirements and methods of satisfying them are well known in the

art and will not be further discussed herein for reasons of brevity.

Fig. 1 schematically shows a lenticular sheet and defines the various

parameters involved in its description. Since the indicia carrier with the

interlaced image printed on it is to be placed in contact with the flat lower

side of the lenticular sheet or panel, the thickness of the sheet is uniform

and is equal to the focal length f of the lenses, in order to satisfy the second

requirement of a lenticular display hsted hereinabove. The focal length

depends on the radius of curvature R. The pitch of the lenses is a chord of

length M of a circle of radius R. Keeping in mind that for practical reasons

it is required that the lenses be kept reasonably flat, it has been found from

experience that lenticular sheets having a uniform thickness f can be constructed for values of M ranging from between about 0.2R to 0.35R.

In known lenticular systems the pitch of both the lenses and interlaced images is a constant, defined as the basic pitch, in order to satisfy the first requirement listed hereinabove. In the present invention the value of the basic pitch is shifted in a

predetermined fashion from one lens to an adjacent lens in at least a part of

the array. The variation in pitch from one lens to the next is small such that

it will not cause a noticeable localized distortion in the basic images of an interlaced image, having the basic pitch, viewed through the lenticular

sheet. The variation in the width of two adjacent lenses can be up to 10%

without causing distortion of the print, but it is preferred to keep the

variation much smaller, on the order of 1%. The accumulated effect of a

series of small variations in the pitch (known as the cumulative pitch) of the

lenses however eventually results in a sufficient difference between the

pitch of the lenses and the basic pitch of the lines of print of the interlaced

image such that the first condition for a lenticular display listed

hereinabove is violated. The maximum allowable difference between the

cumulative pitch of the lenses and that of the printing, such that it is still

possible to view the basic images, is defined as the tolerance of the basic

pitch. The tolerance is dependent on the number of basic images and when

this tolerance is exceeded it becomes impossible to view the basic images.

The largest value of the tolerance is about 50% of the basic pitch, for the

case of an interlaced image composed of two basic images.

According to the invention, the computer program used in the last phase of

the process of producing the interlaced image is adjusted to vary the width of the fines of the interlacing in accordance with the variable pitch of the

lenses on the lenticular sheet. When this is done, there is agreement at all

points between the pitches of the lenses and the underlying printing and

therefore the basic images can be viewed.

The following example, shown in Fig. 2, is provided merely to illustrate the

invention and is not intended to limit the scope of the invention in any

manner.

In Fig. 2 is shown an example of a lenticular lens sheet according to the

invention. The lens sheet has 30 lenses and a pitch that varies from 1.1 to

1.468 mm. The pattern for the variations of the pitch is a simple geometric

progression in which the pitch of each lens is 1.01 times that of the lens that preceded it. In this way a series of lenses is constructed such that the

difference between adjacent lenses is barely noticeable, however the

cumulative change in the pitch, when compared to a sheet with constant

basic pitch, is 0.368. This change in pitch value of over one third is greater than the tolerance of the basic pitch and therefore enough to distort

completely the images of an interlaced image printed with constant basic

pitch viewed through the lens sheet of Fig. 2.

If, however, the interlaced image is prepared according to the same geometric progression as that used for producing the variable pitch of the lenses, it will be possible to place it under the lens sheet of Fig. 2 and the

line of print viewed through a given lens will alternately be that having the

same pitch as the lens and that of a neighboring fine, having an

indiscernibly different pitch.

From this example it can be seen that it is enough to alter the pitch of about

30 lenses located in the middle of a lenticular sheet to lead to a total

disruption of the display.

The present invention therefore leads to a relationship between the lens

sheet and the interlaced image that must be satisfied if the basic images are

to be viewed. Any type of pattern, random or according to a mathematical

formula, can be used for varying the pitch, the only requirement being that

the change from lens to lens is small and that the accumulated variation

eventually lead to total cumulative pitch is greater than the tolerance of the

basic pitch.

Any one who has in his possession, for example, a lenticular sheet, according

to the method of the invention, will not be able to use it with a printed

interlaced image having a constant pitch or even having a variable pitch created according to the method of the invention but with a different pattern from that of the lenticular sheet. Additionally, reverse engineering to modify

a print program to conform to a lens sheet of the invention without knowledge of the rule governing the changes in the lens sheet is virtually

impossible.

Although embodiments of the invention have been described by way of illustration, it will be understood that the invention may be carried out with

many variations, modifications, and adaptations, without departing from its

spirit or exceeding the scope of the claims.

Claims

1. A method for generating a printed interlaced image and lenticular sheet

or panel combination which comprises the steps of:

a) creating a transparent lenticular sheet or panel comprising

linear lenses having a basic pitch; wherein, at least a portion of

said sheet or panel comprises a plurality of lenses having

variable pitches resulting in a given cumulative pitch; b) processing said printed interlaced image in a way that the

pitch of the interlaced print is variable in accordance with the

variable pitch of said lenses on said lenticular sheet or panel.

2. A method according to claim 1, wherein the difference between the

cumulative pitch of the lenticular sheet or panel is different from the

cumulative pitch of the interlacing by an amount that exceeds the

tolerance of the basic pitch.

3. A method according to claim 1, wherein the cumulative pitch distance of

the sheet or panel having variable lenses is different than the cumulative pitch distance of a hypothetical sheet, comprising uniform lenses having

the same basic pitch by a factor of at least half of said basic pitch.

4. A method according to claim 1, wherein the progressive variation

between two adjacent lenses is less then 10% of the width of one of the

lenses.

5. A method according to claim 1, wherein the variation of the pitch of the

lenses and of the complementary interlaced print corresponds to a

mathematical formula.

6. A method according to claim 1, wherein the variation of the pitch of the

lenses and of the complementary interlaced print is random.