DE19955383A1 - Method for applying color information to an object treats the object by laser radiation with a vector and/or grid method using a two-coordinate beam-deflecting device and a focussing device for focussing laser radiation on a layer. - Google Patents

Abstract

An object has two types of color-generating particles in a near-surface layer that alter the color of this layer through the effect of laser radiation (1-3) applied with two or more different wavelengths. The object is treated by laser radiation with a vector and/or grid method using a two-coordinate beam-deflecting device (6) and a focussing device (7) to focus radiation on a layer of the object, beams being guided through these devices by a beam-guiding device (8).

Description

The invention relates to a method for applying colored information to an object. For this type of method, the object has at least one layer close to the surface with at least two different coloring particles which change the color of this layer under the influence of laser radiation. Laser radiation with at least two different wavelengths (λ ₁ , λ ₂ , λ ₃ ) is used to change the color of this layer. Laser radiation is applied to the object in the vector and / or raster process via a two-coordinate beam deflection device and a focusing device. The focusing device focuses the laser radiation on the layer of the object that contains the coloring particles. A color change occurs locally (in the laser focus) at the locations of the object provided for the colored information.

From DE 30 48 736 C2 it is known to laser cards plastic cards label, the plastic cards at least in a layer close to the surface for For the purpose of this labeling, special laser additives contain as coloring particles: On An example of such a laser additive is the laser additive with the brand name Iriodin LS 825 from Merck. This pigment is transparent to light gray in itself. As a result of This laser additive is exposed to laser radiation of 1064 nm (Nd-YAG laser) triggered an intense, irreversible color-changing reaction in the plastic. The reaction usually causes the plastic to darken (black), caused by carbonization of the plastic polymer matrix. The laser additive causes an absorption of the laser radiation necessary for carbonization, whereby Laser additives are used, their absorption to a corresponding laser wavelength is coordinated.

In addition, it is known to use so-called latent pigments as coloring particles use that are at least almost transparent in themselves. When applied with Laser radiation, however, becomes the absorption property of the latent pigment  changed that the pigment has an absorption in the visible after laser irradiation Has spectral range, causing a color change in the layer in which this pigment is caused.

Furthermore, WO 96/35585 describes a method for applying colored information known in which three different pigments are used as color-imparting particles each at least at one point (for a certain wavelength or wavelength range) absorb light in the visible spectral range (400 nm to 700 nm). When irradiated with intense laser radiation with a certain wavelength, preferably the wavelength, where the absorption of the pigment is strongest, these pigments lose theirs Absorption property at least partially. You can at least partially bleach this way. By wavelength-selective bleaching using laser radiation, one can locally Color adjustment done.

Ideally, the layer on which the colored information is to be applied has the following pigments (colorants):

• - a first pigment that mainly absorbs blue light (440 nm) - the The color of this pigment is yellow,
• - a second pigment that mainly absorbs green light (532 nm) - the The inherent color of this pigment is red (magenta),
• - a third pigment that mainly absorbs red light (660 nm) - the The intrinsic color of this pigment is blue (cyan).

Are these pigments equally distributed in a layer in almost the same concentration present, this layer appears black when viewed in sunlight. By Wavelength selective bleaching by means of laser radiation of the individual pigments can be done adjust the color of the layer in a targeted manner by subtractive color mixing. If you e.g. B. the layer is irradiated at one point with laser radiation of 440 nm and the first pigment completely bleached, you get a layer that no longer absorbs blue light, but only green and red light. The color impression is also corresponding this place.  

In order to be able to adjust the color over a wide range using this method, it is required the appropriate layer of the object with laser radiation different To apply wavelength.

For this purpose it is proposed in WO 96/35585 to use a tunable laser, which is able to generate laser radiation of different wavelengths. The The object is exposed to laser radiation in vector and / or Screening method using a two-coordinate beam deflector and one Focusing device. The focusing device focuses the laser radiation on the Layer of the object that contains the coloring particles. One problem here is however, that the intensity of tunable lasers is often too low. Besides, is The operating state of tunable lasers is often not stable because these lasers are very depend sensitively on external conditions. A continuous operation under Production conditions cannot be achieved with a tunable laser.

It is also proposed in WO 96/35585 for the application of colored information to use three different laser systems on one object - for each wavelength a laser system. The first pigment is bleached in a first process step. Then the object must be transported to the second laser system, where then the second pigment is bleached, etc. However, there are some disadvantages. Firstly, the transportation of the object from one laser system to the next is complex and time consuming. In addition, the item must be repositioned in every laser system be, which is very difficult because the positioning accuracy by the size of the pixels (approx. 50 to 100 µm) of the information to be applied is given. Second, everyone requires Laser system has its own two-coordinate beam deflection device and an associated one Focusing device to act upon the object in vector and / or To be able to perform screening processes.

The object of the invention is to provide a method for applying colored information to create an object using laser radiation of different wavelengths that is simple, can be carried out reliably and quickly.  

This object is achieved by the characterizing features of Claim 1 solved. The subsequent sub-claims contain advantageous embodiments of the method.

According to the invention, at least one beam guiding means is provided to direct a first laser beam with the wavelength (λ ₁ ) and at least one further laser beam with a wavelength (λ ₂ ), which differs from the wavelength of the first laser beam, via the two-coordinate beam deflection device and the focusing device to guide the layer of the object in which the coloring particles are located.

The method according to the invention compared to the use of a tunable Lasers the advantage that a for each laser wavelength to generate the laser radiation own stable, powerful laser beam source can be used. About the According to the invention, the beam generating agents provided are those based on their different production location spatially separated laser beams different wavelength over a two-coordinate beam deflector and the one focusing device is directed to the layer of the object to be labeled.

The method according to the invention has three different uses Laser systems have the advantage that the object is not designed for exposure to Laser radiation of different wavelengths transported from one laser system to the next must become. Handling systems for the further transport of the item from one Laser system to the next is eliminated. There is also time due to the lack of transport saved. In particular, there are no positioning problems due to the onward transport.  

The invention will be further explained below with the aid of the attached drawings. It shows:

Fig. 1 is a diagram for a real absorption layer in which different bleachable by laser radiation, coloring particles are located,

Fig. 2 shows an idealized absorption diagram for a layer in which means. There are bleachable, coloring particles

Fig. 3- Fig. 5 bleaching diagrams for three different coloring particles,

Fig. 6 shows a first method and according assembly,

Fig. 7 shows the beam profile of two focused laser beams of different wavelength in the range of to be inscribed layer,

Fig. 8 is a detailed view of the first process according to the arrangement,

Fig. 9 shows a second method and according assembly,

Fig. 10 shows a third method and according assembly,

Fig. 11 shows a fourth method according assembly,

Fig. 12 is a lens system for compensating the chromatic aberration of the focusing device parallel to the optical axis,

Fig. 13 shows a fifth method and according assembly,

Fig. 14 is a view for explaining the lateral chromatic error of the focusing device,

Fig. 15 is a step index fiber with a lens behind the extraction end of the fiber,

Fig. 16 is a section through a step-index fiber having the profile of the refractive index,

Fig. 17 shows the beam profile of a Gaussian-shaped beam before coupling into a step-index fiber and after the extracting,

Fig. 18 is a plan view of the layer of the article to be inscribed with the image points,

Fig. 19 is a table of control data for the novel process.

In Fig. 1 a real absorption spectrum is shown of an inventive be inscribed layer of an object. In the following, labeling is always understood to mean the application of colored information. This layer contains three coloring particles (also called colorants), whose absorption behavior is different in the visible spectral range. The absorption bands are not ideally separated from one another. In the area where colorant 1 mainly absorbs, colorants 2 and 3 also absorb, albeit to a much lesser extent. In the area where the colorant 2 mainly absorbs, there is also little absorption for the colorants 1 and 3 . Only in the area where the colorant 3 mainly absorbs is there hardly any absorption of the other two colorants. An example of the colorant 1 is the pigment with the trade name Novoperm Gelb HR 70 from Clariant. An example of the colorant 2 is the pigment with the trade name Hostaperm Rosa E from Clariant. An example of the colorant 3 is the pigment with the trade name Monastral Blau FGX from Clariant. Common to these pigments is that they can be bleached under the influence of laser radiation. By wavelength-selective bleaching, the color of the layer can be adjusted by subtractive color mixing. From a statistical point of view, each surface element of the layer has an equal distribution of the different coloring particles. On the one hand, the wavelengths that are used for bleaching the individual colorants are adapted to the absorption spectrum, on the other hand, the colorants used and their composition are selected based on which laser wavelengths are the cheapest available. The resulting color of the layer therefore depends on which colorants are used, with which laser wavelengths and with which laser intensity each is bleached. The latter, the respective laser intensity, has a great influence on the degree of bleaching. This is illustrated in Figures 3-5 where the bleaching diagrams for three different colorants are shown. The dependence of the degree of bleaching on the laser intensity is different for each colorant. This fact is taken into account - as described below - by a special process control. No bleaching takes place below a threshold intensity. Above this threshold intensity there is a range that is linear to a first approximation and then changes into a saturation range. Above a certain laser intensity, the layer is then destroyed.

In the example above, laser beams with the following wavelengths were used: 440 nm, 532 nm and 660 nm. The laser beam with 532 nm is by means of an Nd-YAG laser generated, the base wavelength of 1064 nm is halved by frequency doubling. The 660 nm laser beam is generated by means of an Nd-YAG laser, the Base wavelength of 1320 nm is halved by frequency doubling. The laser beam with 440 nm is generated by means of an Nd-YAG laser, the base wavelength of 1320 nm is reduced to a third by tripling the frequency. The types of Frequency multiplication are known to the person skilled in the art. These laser beam sources run stably and provide adequate performance.

However, the method according to the invention is not based on the use of laser beams limited to these wavelengths. The method according to the invention is also not based on Method of wavelength selective bleaching limited, but also to the Laser irradiation of latent pigments and / or on the inscription laser-induced carbonization applicable. Accordingly, the laser wavelengths are too choose.

In FIG. 6, a first method and according assembly is shown. The beam guiding means ( 8 ) provided according to the invention has a first optically reflecting element ( 8 A) which reflects laser radiation of a first wavelength (λ ₁ ) and transmits laser radiation with at least a second wavelength (λ ₂ , λ ₃ ), wherein

• - The first laser beam ( 1 ) with the wavelength (λ ₁ ) is reflected by the reflecting element ( 8 A) in the direction of the two-coordinate beam deflection device ( 6 ),
• - At least one second laser beam ( 2 ) with a wavelength (λ ₂ ) is transmitted through the reflecting element ( 8 A) to the two-coordinate beam deflection device ( 6 ).

The optically reflective element ( 8 A) is a dielectric mirror or a dielectric reflection prism (not shown). Dielectric mirrors or dielectric reflection prisms, which reflect radiation of a specific wavelength or a specific wavelength range and are otherwise at least partially transparent, are known to the person skilled in the art. In this way, the first laser beam with a wavelength of 440 nm and a second laser beam with a wavelength of 532 nm, which are generated spatially separated from one another, are guided onto one and the same two-coordinate beam deflection device ( 6 ). The second laser beam can be directed at the first reflective element ( 8 A) directly or via a further reflective element ( 8 B) - as shown. The angle of reflection in the illustrated embodiment is 45 °. However, other reflection angles are also provided, the arrangement of the two-coordinate beam deflection device ( 6 ) and the focusing device ( 7 ) being chosen with a view to the relative position of the reflecting element ( 8 A) and with a view to the reflection angle. After the reflecting element ( 8 A), the two laser beams ( 1 , 2 ) preferably run along a line. If a third laser beam with a wavelength of 660 nm is to be coupled in, the second laser beam is reflected by the second reflective element ( 8 B) in the direction of the first reflective element ( 8 A) and through it onto the two-coordinate beam deflection device ( 6 ) transmitted. The third laser beam ( 3 ) with a wavelength (λ ₃ ) is then transmitted through the first and second reflecting element ( 8 A, 8 B) onto the two-coordinate beam deflection device ( 6 ). For this purpose, the first and the second reflecting element ( 8 A, 8 B) are at least partially transparent to the wavelength of the third laser beam. The third laser beam can be directed directly or via a further reflecting element ( 8 C) - as shown - onto the second reflecting element ( 8 B).

In FIG. 8 is a detailed view of the first method according to an arrangement is shown. As can be seen, the laser beams experience a beam offset due to the reflecting elements ( 8 A, 8 B). This beam offset is taken into account by appropriately setting the points of incidence of the laser beams on the reflecting elements, so that the various laser beams then run along a line. The position of the reflective elements ( 8 A, 8 B, 8 C) is preferably adjustable.

The chromatic aberration of the focusing device ( 7 ) parallel to the optical axis (A) of the focusing device will be explained with reference to FIG. 7. This is a fundamental problem that arises when laser beams of different wavelengths are to be focused by one and the same focusing device ( 7 ). Such a focusing device ( 7 ) is a lens or a lens system, preferably a flat field lens. Such a flat field lens now has a chromatic aberration which causes problems when the object ( 4 ) to be labeled is exposed to laser radiation of different wavelengths. Chromatic aberration means that rays with a smaller wavelength are refracted more than rays with a longer wavelength. The consequence of this is that the focal length (f) is wavelength-dependent, the difference in focal length between a blue laser beam (440 nm) and a red laser beam (660 nm) being able to be 2 to 3 mm. The manufacturer's specifications for wavelength-dependent focal lengths always refer to laser beams with the same beam characteristics (vanishingly low divergence and same beam diameter) before focusing. The thickness of a typical plastic card is e.g. B. 0.8 mm. The focal length difference is therefore already a multiple of the card thickness, while the labeling according to the invention is to take place in a layer ( 4 A) close to the surface. In Fig. 7, the distance of the surface to be labeled ( 4 A) from the plane field lens is chosen so that the focus for the laser radiation with the wavelength of 440 nm is on the surface to be labeled. The focus of the laser spot is also not arbitrarily small, but has a finite size due to diffraction (typical value: 50 µm). Without further measures, the focus for the laser radiation with the wavelength of 660 nm is then 2 to 3 mm below the card surface ( 4 A). This in turn has the consequence that the laser intensity for the laser radiation with the wavelength 660 nm on the card surface ( 4 A) is not high enough to achieve a color change. 2 to 3 mm above the focus, the beam diameter is approximately twice as large as in focus, so the intensity there is only a quarter of the intensity in focus. With most laser additives, a color change outside of the focus cannot be achieved, since the laser intensity there is less than the threshold intensity.

In order to address the above-described problem of chromatic aberration, is a laser beam having the wavelength (λ) in front of the focusing means (6) means (9) is provided for compensating the chromatic aberration according to the invention at least in the beam path. This means ( 9 ) changes the beam characteristic of the laser beam (s) so that they all have their focus in the area ( 4 A) of the object to be labeled, which is near the surface. The following procedure is envisaged: The distance of the area to be labeled ( 4 A) from the plane field lens ( 6 ) is selected so that the green laser beam with the wavelength of 532 nm has its focus on the area to be labeled ( 4 A) without further means . So that the other two laser beams then have their focus there, corresponding optically effective means ( 9 ) are used in their beam path. Which of the laser beams ( 1 , 2 , 3 ) is selected as the starting point for the selection of the flat field lens ( 6 ) and the distance to the surface to be labeled ( 4 A) depends on the specific conditions. Appropriate means ( 9 ) for compensating the chromatic aberration are then necessary for the other laser beam (s ) ( 1 , 2 , 3 ). Provision is also made for a means ( 9 ) for compensating the chromatic aberration to be provided for each laser beam ( 1 , 2 , 3 ).

The means ( 9 ) for compensating for the chromatic aberration of the focusing device parallel to the optical axis (A) of the focusing device is preferably formed by a lens or a lens system. Such a lens system is shown in FIG. 12, consisting of a diverging lens ( 9 A) and a converging lens ( 9 B), the distance (d) between these two being preferably adjustable by one for each laser beam ( 1 , 2 , 3 ) to give different divergence. The respective laser beam first passes through the diverging lens ( 9 A) and then through the converging lens ( 9 B) before it is guided further onto the two-coordinate beam deflection device ( 6 ) and the focusing device ( 7 ). For example, the blue laser beam (440 nm) is widened a little in the direction of the focusing device, while the red laser beam (660 nm)) is bundled a little in the direction of the focusing device. With this measure, all three laser beams (red, green and blue) ultimately have their focus on the surface to be labeled ( 4 A).

The means ( 9 ) for compensating the chromatic aberration can also be a glass fiber ( 11 ) and a converging lens ( 9 ) (cf. FIG. 15). For this purpose, the corresponding laser beam ( 1 , 2 , 3 ) for which compensation is to be carried out is passed through a glass fiber ( 11 ), through which it then emerges divergent. It can now be bundled again using the converging lens ( 9 ). By varying the distance between the fiber end and the converging lens ( 9 ), the position of the focus behind the focusing device ( 7 ) is also changed. To compensate for the chromatic aberration, the distance between the fiber end ( 10 A) and the two-coordinate beam deflection device ( 6 ) can also simply be set in each case (cf. FIG. 13). It shows how three laser beams ( 1 , 2 , 3 ) of different wavelengths are each directed via a glass fiber ( 10 ) to a deflection mirror ( 6 A) of the two-coordinate beam deflection device ( 6 ), the distances between the fiber ends ( 10 A) Deflecting mirrors ( 6 A) are different. This ensures that all laser beams have an almost common focus on the surface to be labeled ( 4 A) despite different wavelengths.

FIG. 9 shows a second arrangement according to the method, in which, in contrast to the arrangement from FIGS. 6 and 8, the three laser beams are not directed parallel to one another at the beam guiding means ( 8 A, 8 B, 8 C) according to the invention. In the arrangement shown in FIG. 9, one of the laser beams ( 3 ) originally runs perpendicular to the other two laser beams ( 1 , 2 ), which originally run parallel and offset from one another. The same dielectric mirrors ( 8 A, 8 B) are used here, which are also provided for the arrangement according to FIGS. 6 and 8.

Fig. 10 shows a fourth method and according assembly. The beam generating means ( 8 ) has an optically reflecting element ( 8 D) which is adjustable in its position, preferably rotatable, and which reflects at least laser radiation of a first wavelength (λ ₁ ) and laser radiation of a second wavelength (λ ₂ , λ ₃ ), wherein

• the first laser beam ( 1 ) with the wavelength (λ ₁ ) and the second laser beam ( 2 ) with the wavelength (λ ₂ ) are offset parallel to one another and / or hit the reflecting element ( 8 D) at different angles,
• the reflecting element (SD) is brought into a first position in order to reflect the first laser beam ( 1 ) with the wavelength (λ ₁ ) in the direction of the two-coordinate beam deflection device ( 6 ),
• - The reflecting element ( 8 D) is brought into a second position in order to reflect the second laser beam ( 2 ) with the wavelength (λ ₂ ) in the direction of the two-coordinate beam deflection device ( 6 ).

The reflecting element ( 8 D) is a metallic mirror or a metallic mirrored reflection prism.

In Fig. 11 a fifth method and according arrangement. The beam guiding means ( 8 ) is a first rotatable, metallic deflection mirror ( 6 A) of the two-coordinate beam deflection device ( 6 ), via which the first laser beam ( 1 ) with the wavelength (λ ₁ ) and at least one second laser beam ( 2 ) with the Wavelength (λ ₂ ) are reflected in the direction of a second rotatable, metallic deflection mirror ( 6 B) of the two-coordinate beam deflection device ( 6 ), which then directs the laser beams towards the focusing device ( 7 ) for focusing the laser radiation onto a layer ( 4 A ) of the object ( 4 ) reflected, wherein

• - The deflection mirror ( 6 A) for the application of the object ( 4 ) with the first laser beam ( 1 ) with the wavelength (λ ₁ ) is rotated by a first offset value,
• - The deflection mirror ( 6 A) for the application of the object () with the second laser beam ( 2 ) with the wavelength (λ ₂ ) is rotated by a second offset value.

In Fig. 14, another fundamental problem is illustrated, which occurs when laser beams of different wavelengths through one and the same plane field lens ( 7 ) for labeling on the surface ( 4 A) of an object, for. B. wants to focus a plastic card. This problem lies in the chromatic aberration of the plane field lens transverse to the optical axis. This means that laser beams of different wavelengths, which pass through the plane field lens ( 7 ) at a certain angle (θ) to the optical axis (A) of the plane field lens ( 7 ), do not strike the same place on the surface to be labeled ( 4 A) as desired, but are laterally offset from each other. In particular when the object ( 4 ) is inscribed on the edge, that is to say relatively far away from the optical axis (A) of the plane field objective (A), the lateral focus offset is particularly large. According to the invention, to compensate for the lateral chromatic aberration of the focusing device ( 7 ) for at least one laser beam with the wavelength (λ) when the rotatable, metallic deflecting mirror ( 6 A, 6 B) is rotated, the two-coordinate beam deflecting device ( 6 ) is applied to a layer ( 4 A) of the object ( 4 ) in the vector and / or raster method takes into account a correction value (Δx, Δy) for the chromatic transverse error.

The colored information to be applied consists of a multiplicity of pixels (P), the object ( 4 ) being acted upon with laser radiation to generate the pixels (P) in pulsed operation. Various procedures are provided according to the invention for generating the individual colored pixels (P).

The first laser beam ( 1 ) can be applied to the object ( 4 ) point by point with a first laser intensity value (I ⁽¹⁾ ), while the second laser beam ( 2 ) can be applied to the object ( 4 ) point by point with a second laser intensity value ( I ⁽²⁾ ) and the point-by-point exposure of the object ( 4 ) to the third laser beam ( 3 ) with a third laser intensity value (I ⁽³⁾ ). It is also provided that the laser intensity is varied from pixel to pixel when the object ( 4 ) is punctually impacted with at least one laser beam ( 1 , 2 , 3 ).

One procedure for the image generation according to the invention is to first apply each of the pixels to be generated in the vector and / or raster method one after the other with the first laser beam ( 1 ), and then then one after the other with at least one second laser beam ( 2 ). to act upon.

Alternatively, pixel by pixel is applied one after the other with laser beams of different wavelengths.

In addition, it is also envisaged that a pixel for a pixel at the same time Laser beams of different wavelengths are applied.

The object ( 4 ) is preferably exposed to laser radiation in such a way that a correction value for the chromatic transverse error is taken into account pixel by pixel.

The starting point for the method according to the invention is an image which is in digital form (for example in the so-called PCX format) or is converted into one. Image is understood to mean both a photo and alphanumeric information, a barcode or the like. The x, y coordinates (x ₁ , y ₁ , x ₂ , y ₂ ) for controlling the two-coordinate beam deflection device ( 6 ) are then derived from this digital image information for each pixel (P1, P2,...). In addition, based on the digital color information about the pixels, laser intensity values (I ₁ ⁽¹⁾ ), (I ₁ ⁽²⁾ ),. , .) derived so that the correct degree of bleaching and thus the correct color impression of a pixel is achieved. In addition, for each pixel (x, y) a correction value (Δx, Δy) is generated to compensate for the lateral chromatic aberration. All of this data can e.g. B. be stored in a table with control data for the method according to the invention (see FIG. 19).

Finally, another problem is to be discussed, which is particularly important in the case of so-called laser bleaching. As can be seen from FIGS. 3 to 5, the degree of bleaching depends strongly on the respective laser intensity. However, it is now the case that the laser beams ( 1 , 2 , 3 ) used generally have a Gaussian beam profile (see FIG. 17) which is also present in the focus (laser writing spot). However, this means that the laser intensity in the laser writing spot is not constant. It is very high in the center of the jet, but decreases sharply towards the edges. This means that uniform bleaching of a pixel cannot be achieved. In the worst case, the intensity at the edges of the pixels is less than the threshold value, so that there is no bleaching at all. To avoid this problem, the laser beams ( 1 , 2 , 3 ) are coupled into a so-called step index fiber ( 11 ). In Fig. 16 a section through a step-index fiber (11) and the rectangular profile of the refractive index. A laser beam with a Gaussian profile coupled into the step index fiber ( 11 ), after it has left the step index fiber ( 11 ) again, has a rectangular intensity distribution over its cross section. The beam profile of the laser is thus an image of the course of the refractive index of the step index fiber. In this way, a laser beam is made available with an almost constant intensity across its cross-section, which is excellently suited for uniform bleaching of pixels.

Reference list

1

first laser beam

2nd

second laser beam

3rd

third laser beam

4th

object

4th

A layer of the object that contains the coloring particles

5

Pixel

6

Two coordinate beam deflector

6

A first deflecting mirror of the two-coordinate beam deflecting device

6

B second deflection mirror of the two-coordinate beam deflection device

7

Focusing device

7

A optical axis of the focusing device

8th

Beam guiding means

8th

A first reflecting element of the beam guiding means

8th

B second reflecting element of the beam guiding means

8th

C third reflective element of the beam guiding means

8th

D rotatable, reflective element of the beam guiding means

9

Lens system to compensate for the chromatic aberration of the focusing device parallel to the optical axis

9

A diverging lens

9

B converging lens

10th

fiber

10th

A coupling end of the fiber

11

Step index fiber

Claims (21)

1. A method for applying colored information to an object ( 4 ), the object having at least two layers ( 4 A) close to the surface having at least two different coloring particles which change the color of this layer ( 4 a) under the influence of laser radiation, in which

• - Laser radiation ( 1 , 2 , 3 ) with at least two different wavelengths (λ ₁ , λ ₂ , λ ₃ ) is used to change the color of this layer ( 4 A),
• - The object ( 4 ) is exposed to laser radiation in the vector and / or raster process via a two-coordinate beam deflection device ( 6 ) and a focusing device ( 7 ) for focusing the laser radiation onto the layer ( 4 A) of the object ( 4 ),

characterized in that
at least one beam guidance means ( 8 ) is provided to transmit a first laser beam ( 1 ) with the wavelength (λ ₁ ) and at least one further laser beam ( 2 ) with a wavelength (λ ₂ ) that is different from the wavelength of the first laser beam to guide the two-coordinate beam deflection device ( 6 ) and the focusing device ( 7 ) onto the layer ( 4 A) of the object ( 4 ). 2. The method according to claim 1, characterized in that the beam guiding means ( 8 ) has at least one first optically reflecting element ( 8 A) which reflects laser radiation of a first wavelength (λ ₁ ) and laser radiation with at least a second wavelength (λ ₂ , λ ₃ ) transmitted, whereby

• - The first laser beam ( 1 ) with the wavelength (λ ₁ ) is reflected by the reflecting element ( 8 A) in the direction of the two-coordinate beam deflection device ( 6 ),
• - At least one second laser beam ( 2 ) with a wavelength (λ ₂ ) is transmitted through the reflecting element ( 8 A) to the two-coordinate beam deflection device ( 6 ).

3. The method according to claim 2, characterized in that a second optically reflecting element ( 8 B) is provided which reflects laser radiation of the wavelength (λ ₂ ) and transmits laser radiation with at least one other wavelength (λ ₃ ), wherein

• - The first laser beam ( 1 ) with the wavelength (λ ₁ ) is reflected by the first reflecting element ( 8 A) in the direction of the two-coordinate beam deflection device ( 6 ),
• a second laser beam ( 2 ) with a wavelength (λ ₂ ) is reflected by the second reflecting element ( 8 B) in the direction of the first reflecting element ( 8 A) and is transmitted through this to the two-coordinate beam deflection device ( 6 ),
• - A third laser beam ( 3 ) with a wavelength (λ ₃ ) through the first and second reflecting element ( 8 A, 8 B) is transmitted through to the two-coordinate beam deflection device ( 6 ).

4. The method according to claim 2 or 3, characterized in that the optically reflective element ( 8 A, 8 B) is a dielectric mirror. 5. The method according to claim 2 or 3, characterized in that the optically reflective element ( 8 A, 8 B) is a dielectric reflection prism. 6. The method according to claim 1, characterized in that
the beam guidance means ( 8 ) is an optically reflecting element ( 8 D) which is adjustable in its position, preferably rotatable, and which reflects at least laser radiation of a first wavelength (λ ₁ ) and laser radiation of a second wavelength (λ ₂ , λ ₃ ), wherein

• the first laser beam ( 1 ) with the wavelength (λ ₁ ) and the second laser beam ( 2 ) with the wavelength (λ ₂ ) are offset parallel to one another and / or hit the reflecting element ( 8 D) at different angles,
• - The reflecting element ( 8 D) is brought into a first position in order to reflect the first laser beam ( 1 ) with the wavelength (λ ₁ ) in the direction of the two-coordinate beam deflection device ( 6 ),
• - The reflecting element ( 8 D) is brought into a second position in order to reflect the second laser beam ( 2 ) with the wavelength (λ ₂ ) in the direction of the two-coordinate beam deflection device ( 6 ).

7. The method according to claim 6, characterized in that the optically reflective element ( 8 D) is a metallic mirror. 8. The method according to claim 6, characterized in that the optically reflective element ( 8 D) is a metallic reflection prism. 9. The method according to claim 1, characterized in that the beam guide means ( 8 ) is a first rotatable, metallic deflection mirror ( 6 A) of the two-coordinate beam deflection device ( 6 ), via which the first laser beam ( 1 ) with the wavelength (λ ₁ ) and at least a second laser beam ( 2 ) with the wavelength (λ ₂ ) is reflected in the direction of a second rotatable, metallic deflection mirror ( 6 B) of the two-coordinate beam deflection device ( 6 ), which then directs the laser beams in the direction of the focusing device ( 7 ) for focusing the laser radiation onto a layer ( 4 A) of the object ( 4 ), wherein

• - The deflection mirror ( 6 A) for the application of the object ( 4 ) with the first laser beam ( 1 ) with the wavelength (λ ₁ ) is rotated by a first offset value,
• - The deflecting mirror ( 6 A) for the application of the object ( 4 ) with the second laser beam ( 2 ) with the wavelength (λ ₂ ) is rotated by a second offset value.

10. The method according to any one of the preceding claims, characterized in that the focusing device ( 7 ) for focusing the laser radiation on a layer ( 4 A) of the object ( 4 ) is a lens or a lens system, preferably a flat field lens. 11. The method according to any one of the preceding claims, characterized in that in the beam path at least one laser beam with the wavelength (λ) in front of the focusing device ( 7 ) for focusing the laser radiation on a layer ( 4 A) of the object ( 4 ) a means ( 9 , 10 ) for compensating the chromatic aberration of the focusing device ( 7 ) is provided parallel to the optical axis of the focusing device. 12. The method according to claim 11, characterized in that the means ( 9 , 10 ) for compensating for the chromatic aberration of the focusing device parallel to the optical axis comprise an adjustable in the beam path lens or an adjustable lens system ( 9 A, 9 B). 13. The method according to claim 11, characterized in that for compensating the chromatic aberration of the focusing device parallel to the optical axis (A) in the beam path of at least one laser beam with the wavelength (λ), a fiber optic ( 10 , 11 ) is provided, through which the Laser beam is guided, the optical path between the coupling end ( 10 A) of the fiber and the focusing device ( 7 ) is adjustable. 14. The method according to any one of the preceding claims, characterized in that to compensate for the chromatic aberration of the focusing device ( 7 ) transverse to the optical axis (A) of the focusing device for at least one laser beam with the wavelength (λ) in the rotary setting of the rotatable, metallic deflection mirror ( 6 A, 6 B) of the two-coordinate beam deflection device ( 6 ) for applying a layer ( 4 A) of the object ( 4 ) in the vector and / or raster method, a correction value (Δx, Δy) for the chromatic transverse error is taken into account. 15. The method according to any one of the preceding claims, characterized in that for at least one laser beam with the wavelength (λ) a step index fiber ( 11 ) is provided in the beam path in front of the two-coordinate beam deflection device ( 6 ), the in the step index fiber ( 11 ) coupled laser beam has a Gaussian beam profile and the laser beam coupled out of the step index fiber ( 11 ) has a rectangular beam profile. 16. The method according to any one of the preceding claims, wherein the color information to be applied consists of a plurality of pixels (P) and the object ( 4 ) is acted upon with laser radiation for generating the pixels in pulse mode, characterized in that

• - The object ( 4 ) is acted upon by the first laser beam ( 1 ) with the wavelength (λ ₁ ) with a first laser intensity value (I ⁽¹⁾ ),
• - The object () is exposed to at least one second laser beam ( 2 ) with the wavelength (λ ₂ ) with a second laser intensity value (I ⁽²⁾ ).

17. The method according to claim 16, characterized in that the application of the object ( 4 ) with laser radiation for generating the pixels is carried out in such a way that the laser intensity is varied from pixel to pixel for at least one laser beam of wavelength (λ). 18. The method according to any one of the preceding claims, characterized in that the application of the object ( 4 ) with laser radiation for generating the pixels (P) takes place in such a way that

• - first of all all the pixels to be generated are successively exposed to the first laser beam ( 1 ) with the wavelength (λ ₁ ) using the vector and / or raster method,
• - Then the pixels (P) to be generated are each successively exposed to at least one second laser beam ( 2 ) with the wavelength (λ ₂ ) in the vector and / or raster method.

19. The method according to any one of the preceding claims 1 to 17, characterized in that
the application of the object ( 4 ) with laser radiation to generate the image points in such a way that
Point by point, laser beams of different wavelengths are applied one after the other. 20. The method according to any one of the preceding claims 1 to 17, characterized in that the application of the object ( 4 ) with laser radiation for generating the pixels (P) is carried out in such a way that pixel by pixel is simultaneously acted upon with laser beams of different wavelengths . 21. The method according to any one of the preceding claims, characterized in that the application of the object ( 4 ) with laser radiation for generating the pixels is carried out in such a way that a correction value for the chromatic transverse error is taken into account pixel by pixel.