LT5964B - Method for production of holographic master - originals - Google Patents

Abstract

Method for production of holographic master-original is related to holography and can be used for producing of holographic master originals by pulsed lasers. The proposed method, by which the unexposed light-sensitive material applied onto the base, is illuminated at the same time focused modulated (object-oriented), and un modulated (supporting) coherent laser light radiation when illuminating by object-radiation on path of the light rays before modulator placed element for formation of latent image and the location of it in respect of lens optical isthmus is defined so that image of latent image forming element, modifying the object radiation intensity focuses in light-sensitive material in recording location of holographic optical element, so as to form in said holographic optical elements micro image, visible with hologram.

Description

The present invention relates to holography and is intended for the production of master holographic originals by pulsed lasers.

TECHNICAL LEVEL

Holograms are widely used for document and product authentication and as exclusive, authentic visual products. There are two stages in the hologram authentication process - user authentication and expert authentication. Because of this, authentic holograms always have features that allow both users and experts to recognize the authenticity of such a hologram. All of these features are first displayed on a hologram called a master holographic original, and then its diffractive structure is transmitted or stamped. , used directly in the production of embossed holograms (in the case of permeability security holograms (Practical Holography, Third Edition, Graham Saxby; Taylor & Francis 2003, pp. 328-333), or copied by contact as described e.g. in WO 2009035310 (Lithuanian Patent LT5573), (for reflection holograms), or the holographic master-original itself can be used as an exclusive product

Thus, the production process of the holographic master-original is very important and its improvement is a pressing task.

One of the main image protection features of the holographic master-original is the 3D or 2D-3D image itself and the micro image seen with special optical equipment. Currently, such means are rendered in transmittance holographic master-originals by computing the desired diffraction grid using computers and recording it either in two intersecting coherent laser beams, either modulated by a spatial light modulator, or by photolithography, or electron beam, on the photosensitive material ( For example, AV Goncharski, AA Goncharski Computer Optics & Computer Holography, Moscovv University Press, 2004.). Therefore, the photosensitive material forms a diffractive structure which, when illuminated, produces a holographic image and, by special means, a secret image. The holographic master-originals thus produced have all the features of a permeability hologram, i.e. the image is visible by illuminating them from the opposite side of the view and has a rainbow distribution or is seen as a color image within a narrow field of vision;

or is visible as a black-and-white image.

Protective reflection holograms are nowadays mostly produced by copying a holographic master-original with images of small real objects. (Optical Document Security by Rudolf L. Van Renesse; Books on Demand, 1994). Because prior to the present invention, there was no known way of imaging the features of reflection in holograms with visualization, the use of dedicated reflective holograms is now rarely used for product and document authentication.

Known state-of-the-art transmittance holographic master-originals require sophisticated computational computing and the exposure of photosensitive material itself takes from a few to several hours. The state-of-the-art methods of recording reflective holographic master-originals cannot incorporate the visual features visible into the image only with the help of special optical equipment.

US Patent No. 7,847,992 discloses a method of producing holographic master-originals wherein the unexposed photosensitive material is applied to the substrate simultaneously illuminated by focused coherent pulsed laser light modulated radiation and unmodulated coherent laser light (reference) radiation when the light is modulated so that the element resulting from coherent modulated and unmodulated laser beam interference would reproduce the hologram image in 3D and / or 3D-2D hologram.

These features are also exhibited by the method of producing holographic master originals described in patent application KR20070072772.

Meanwhile, from the Lithuanian patent no. The 4842 family (US7423792, US7800803) is a prominent class of digital holographic printers capable of recording large format (A5 to lxl, 5m) digital image holograms with a high depth of field print and significantly accelerating the process of producing digital holograms. In this holographic master-original production method, the light modulator is illuminated by a spatial image formed from pixels taken from corresponding hundreds of 3D scenes, the light modulator is illuminated by a coherent pulsed laser light beam, the modulated radiation is focused by a special lens having an optical angle a photosensitive material is placed immediately behind the fold. The photosensitive material is illuminated by a pulse of modulated light, together with an unmodulated support beam of laser light, and a small holographic optical element (HOE) is incorporated into a small area of photosensitive material known as a holopixel or hogel. After chemically or otherwise processing the photosensitive material and illuminating the HOE light recorded in a manner identical to that of the unmodulated laser light at the time of recording, the HOE will "project" the same spatial light modulator image from multiple hundreds of view the scene so that only one pixel image is projected in each direction.

Covering the entire surface of the photosensitive material with such HOEs behaves like a regular hologram - i.e. at different angles of its viewing, slightly different parallax-linked images of the same 3D scene are visible, and the brain of an observer looking at such material with two eyes perceives the visual as spatial. Digital holograms recorded in this way require relatively little computation and are produced by pulsed lasers, which significantly speeds up the production of digital holograms.

Typically, digital image holograms recorded in this way are reflection holograms (i.e., illuminated by the observer), although Lithuanian patent no. 4842 (or U.S. Patent No. 7,800,803) mentions the possibility of writing throughput holograms in this manner. However, transmission and reflection protective holograms made from the resulting digital hologram, the master holographic master, while having a spatial imaging depth that is not available in other spatial imaging holograms, would have only one feature of the protective hologram, a 3D or 2D-3D holographic image. fully used for document and product authentication and as authentic visual products.

This patent from Lithuanian patent no. The known method of manufacturing master-originals 4842 is the closest to the present invention.

The object of the present invention is to improve the method of recording digital holograms so that along with the 3D and / or 2D-3D image, the digital hologram has other features of visual authentication that are only visible with the help of special optical equipment. In this way, the digital holograms thus produced could be used as holographic master-originals for the production of embossed and reflective protective holograms, or the holographic master-original itself could be used as an exclusive product and would have a shorter production time than other known holographic master-originals. time.

THE SUBSTANCE OF THE INVENTION

The object is achieved by a method of applying unexposed photosensitive material to a substrate while simultaneously illuminating with focused coherent pulsed laser light modulation and unmodulated coherent laser light (backing) radiation, where the modulated light is modulated by holographic optical elements. modulated and unmodulated laser beam interference, which would reproduce the hologram image in 3D and / or 3D-2D holograms. What's new is that when illuminated with focused coherent pulsed laser light modulated radiation, it places a stealth imaging element in the light beam path ahead of the modulator and selects its location relative to the optical rotation of the lens so that the streaming imaging element changes coherent laser in the photosensitive material at the point of insertion of the holographic optical element, thereby forming a micro-image visible in said holographic optical elements together with the hologram image by means of special optical equipment (lens, microscope, etc.).

If the exposed pixel and then modulated coherent pulsed laser radiation and non-modulated coherent pulsed laser radiation intersect at the same side of the photosensitive material, it records the transmittance holographic master-original.

If the exposed pixel and then the modulated coherent pulsed laser radiation and the non-modulated coherent pulsed laser radiation intersect at the opposite sides of the photosensitive material, it records the reflection holographic master-original.

The photosensitive material can be illuminated by multiple color coherent pulsed laser beams simultaneously or sequentially.

The secret imaging element may be a liquid crystal reflection or transmittance display or slide, or an image thereof, transmitted to a selected location as above, may be used to focus its image on the photosensitive material. Video streaming or image transfer can be used.

Other objects of the invention are a master original produced in the manner of the present invention and a hologram with a recorded covert image produced from such a master original.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a proposed holographic master-original recording scheme for transmission and reflection master-origin recording (top view), it is clear to those skilled in the art that instead of a skipping surround light modulator, the present scheme may be modified to operate with a reflective surround light modulator.

FIG. 2 shows an example of an image transmitted in a surround light modulator during recording of a single holographic optical element in a holographic master-bandwidth transmission.

FIG. 3 shows an example of an image illuminated by a spatial light modulator during recording of a single holographic optical element in the case of a reflection holographic master-original.

FIG. 4 shows an example of an image transmitted in a secret imaging element during recording of a single holographic optical element in transmission and reflection in holographic master-originals.

FIG. Figure 5 shows how holographic optical elements cover a desired area of photosensitive material.

EXAMPLE OF IMPLEMENTING THE INVENTION

The proposed method may be implemented by the device shown in Figs. 1. It consists of a light source pulsed laser 1, a semitransparent mirror 2 positioned in its beam path, distributing the light flux to the objective reflection from the mirror 2 and a support passing through the mirror 2. The objective light flux is transmitted by the mirrors 3 through the scattering-focusing module 4. , a secret imaging element 5 (which may also be part of a diffusion-focus module), a collimating lens 6, a modulator 7, a special lens 8, (e.g., a lens similar to that described in U.S. Patent No. 4,842 (or U.S. US7800803) having an optical strain on its exterior, where a light-sensitive material 10 is applied immediately behind the strain in its objective beam 9 on a solid or flexible substrate 11. The beam of light is transmitted by mirrors 12 through a beamformer 13 which forms a support beam; mirrors 14 transmitted from the same light on the transducer side of the transmittance in the case of master-original recording 15 or on the opposite side of the photosensitive plate in the case of the reflection master-original 16, formed by a reference beamformer 13 so as to illuminate the photosensitive area close to the illuminated area 9. Usually the shape of the illuminated area is a rectangle, although it should be clear to one skilled in the art that the illuminated area may also be in the shape of another regular polygon.

The substrate 11, on which the photosensitive material 10 is applied, may be transparent in transmittance master-original recording and opaque in reflection in master-original recording, is placed on computer controlled sliders sliding in directions 17 and 18 (direction 18 is vertical in Figure 1). planes) (computer controlled sliders Fig.l not shown).

The proposed method is implemented by this device in the following order.

The unexposed photosensitive material 10, when applied to a solid or flexible, transparent or, in the case of a master-original of holographic transmission, a possibly opaque substrate 11, is placed on a slider in computer controlled directions 17 and

18 (direction 18 is vertical to the plane of Fig. 1) (computer controlled sliders Fig. 1) to illuminate two coherent laser beams: objective beam 9 and support beam 15 (in the case of transmitting holographic master-original production) or support beam 16 ( in the case of reflection master-original production).

The reflected coherent pulsed laser light beam of the system of mirrors 2 and 3 passes through a light-sensitive layer through a scattering-focusing module 4, a secret imaging element 5, a collimating lens 6, a modulator 7, a lens 8, becoming a focused and modulated objective light beam 9, respectively. 10. The spatial light modulator 7 illuminates an image to form a holographic optical element, an example of which is illustrated in FIG. 2 (in the case of a master bandwidth original) and FIG. 3 (for reflection master-original).

The secret imaging element 5 illuminates the image by varying the intensity of the coherent laser light radiation which forms the visual authentication features in the holographic optical element, an example of which is shown in FIG. 4. The position of the secret imaging element 5 is selected such that the lens 8 focuses the illuminated image of the modulator 7 on the photosensitive material 10 at the point of insertion of the holographic optical element, thereby forming a micro-image visible with said hologram image.

Meanwhile, the unmodulated coherent pulsed laser radiation from the mirror system 2, 12, passing through the radiation shaper 13, at the I position of the reflecting mirror 14 reaches the photosensitive material on the same side as the objective beam when recording the transmittance holographic master5 original or reflective mirror 14 II. position accesses photosensitive material from the opposite side when recording the reflection holographic master-original.

During exposure, the photosensitive material 10 is uniformly moved in the direction 17 such that after each pulse of laser radiation, it passes a distance equal to the edge of the illuminated surface of the reference radiation in the scrolling direction (when its illuminated area is rectangular). When the illuminating area of the reference beam is of regular polygonal shape, the photosensitive material shall, after exposure, be at a distance equal to the peripheral direction of the rectangle into which the said polygon may be enclosed.

By exposing one row in the direction 17, the photosensitive material is shifted in the direction 18 at a distance equal to the edge of the illuminated surface of the reference radiation in the direction of scrolling (when its illuminated area is rectangular); when the illuminating area of the reference beam is of regular polygonal shape, the photosensitive material is displaced at a distance equal to the edge of the rectangle to which said polygon may be enclosed; and sequentially exposing as shown above, FIG. 5, which shows a coating of a holographic masteroriginal surface with holographic optical elements that will form a microscope, visible with a magnifying glass or microscope, along with a hologram image.

The coherent laser beam from laser 1 is provided by mirrors 3 and semi-transparent mirror 2 to the stealth imaging element 5. It should be apparent to one skilled in the art that the laser beam may be directed to the coherent laser scattering-focusing module 4 also by other mirror arrangement and that the stealth imaging element can also be placed inside the scatter focus module.

Shape beams 15 and 16 are formed by a beamformer so that they illuminate in the photosensitive area an area close to the area illuminated by the objective beam 9. Normally, the area of illumination is rectangular, although it should be clear to the skilled person that the illuminated area may also be other. of regular polygon shape.

Mirrors 14 are used to direct the formed support beam to the photosensitive material (it should be apparent to those skilled in the art that the formed laser beam may also be directed to the photosensitive material using a different mirror arrangement).

The coherent laser radiation to the beamformer 13 is led away from the laser 1 by mirrors 12 (it should be apparent to one skilled in the art that the laser beam may be led to the beamformer 13 also by other mirror arrangement).

The objective / support beam ratio can be changed using, for example, waveguides and polarizers mounted at any point in the beam path (Fig. 1 not shown).

The master-original obtained by the process of the invention is characterized in that each 3D imaging holographic optical element (holopixel or hogel) contains a secret image, which is visible by special optical means (magnifying microscope).

The digital holograms thus produced can be used as master holographic originals in the manufacture of embossed and reflective protective holograms, or the holographic master original itself may be used as an exclusive product.

Tests have shown that the proposed method enables you to record e.g. 25x30mm master-originals with deep 3D holographic imaging in 20 minutes, while advanced master-hologram recording equipment - electron beam master-hologram recording - would produce a similar, but not so deep, master-original for at least 24 hours [ A. V. Goncharski, A. A. Goncharski Computer

Optics & Computer Holography, Moscow University Press, 2004.]. In addition, the electron beam master hologram recording equipment is unable to achieve the master image depth of the proposed method.

Thus, the proposed method of recording master holograms not only enables the production of a deeper 3D image master image compared to the closest known one, but also incorporates micro-text or secret image visible with special optical equipment, which significantly improves the user and security features of the master holograms. -original made according to the proposed method.

Claims (4)

1. A method of producing holographic master originals by illuminating the unexposed photosensitive material simultaneously with a focused coherent pulse 5 laser light modulated by radiation and unmodulated by a coherent laser Light (Supporting) radiation, when light is modulated such that a set of holographic optical elements resulting from coherent interference between modulated and unmodulated laser beams produces a holographic 3D and / or 3D-2D hologram image, 10 that, when illuminated by focused coherent pulsed laser light modulated radiation, it places a secret imaging element in the path of the light beam before the modulator and selects its location relative to the optical rotation of the lens so that the image of the secret imaging element changing the coherent laser 15 in the photosensitive material at the point of insertion of the holographic optical element, thereby forming in said holographic optical elements a microprint seen with the hologram image. 2. The method of claim 1, wherein the sensitive image is affected The 20 elements and then the modulated coherent pulsed laser radiation and the unmodulated coherent pulsed laser radiation intersect in the photosensitive material on the same side, thereby recording the transmittance holographic master-original. 25th 3. The method of claim 1, wherein the exposed pixel and then modulated coherent pulsed laser radiation and non-modulated coherent pulsed laser radiation intersect at the opposite sides of the photosensitive material, thereby recording a reflection holographic master-original. 4. A method according to any one of claims 1 to 3, characterized in that the photosensitive material can be illuminated simultaneously by several colors of coherent pulsed laser radiation. 10th 5. Method according to any one of claims 1 to 3, characterized in that the photosensitive material can be illuminated sequentially by multiple color coherent pulsed laser radiation. 5 6. Method according to any one of claims 1 to 3, characterized in that the secret imaging element is a reflection or transmission of liquid crystals. display. 7th A process according to any one of claims 1 to 3, wherein the process is covert 10th the imaging element is a slide. 8th A process according to any one of claims 1 to 3, wherein the process is in place the secret imaging element uses its image. % 15 9. The holographic master-original produced by the process of any one of claims 1 to 8. A hologram with a secret image produced from a master original according to claim 9.