ULTRASHORT LASER MICRO-TEXTURE PRINTING

• US 20140185065A1
• Filed: 03/05/2014
• Published: 07/03/2014
• Est. Priority Date: 01/23/2007
• Status: Active Grant

• Current Assignee: IMRA America Incorporated (Aisin Corp.)
• Original Assignee: IMRA America Incorporated (Aisin Corp.)
• Inventors: Shah, Lawrence, Fermann, Martin E.
• Granted Patent: US 8,995,029 B2
• Time in Patent Office: Days
• US Class Current: 358/1.7
• CPC Class Codes: B23K 26/352 for surface treatment
• CPC Class Codes: B41J 2/442 using lasers
• CPC Class Codes: B41J 2/471 using dot sequential main scanning by means of a light deflector, e.g. a rotating polygonal mirror
• CPC Class Codes: G06K 15/1209 Intensity control of the optical beam G06K15/1223 takes precedence
• CPC Class Codes: G06K 15/129 Colour printing
• CPC Class Codes: H04N 1/40037 the reproducing element being a laser
• CPC Class Codes: H04N 1/407 Control or modification of tonal gradation or of extreme levels, e.g. background level

Abstract

Systems and methods for providing laser texturing of solid substrates are disclosed. The texturing may be used to provide grayscale images obtainable from substrates, which may include steel, aluminum, glass, and silicon. In some embodiments, images may be obtainable from the substrate by modifying the reflective, diffractive, and/or absorptive features of the substrate or the substrate surface by forming random, periodic, and/or semi-periodic micro-structure features on the substrate (or substrate surface) by an ultrafast laser pulse train. The ultrafast pulse train may be modulated in order to vary, for example, optical exposure time, pulse train intensity, laser polarization, laser wavelength, or a combination of the aforementioned. The ultrafast pulse train and the substrate may be scanned with respect to each other to provide different optical energies to different regions of the substrate (or substrate surface). In some embodiments, the image is provided by making one or more passes of the ultrafast laser pulse train relative to the substrate.

Claims

1. A method of modifying a medium so that a grayscale image is obtainable from the medium, the method comprising:

providing a medium having a surface;

scanning a laser beam relative to the surface, the laser beam comprising a plurality of optical pulses having a pulse width less than about 100 picoseconds, the laser beam delivering optical energy to the surface of the medium; and

varying the optical energy delivered to different regions of the surface of the medium, thereby altering at least one of reflectivity, absorptivity, or diffractive properties of the regions to provide the grayscale image obtainable from the medium,

wherein at least a portion of said plurality of pulses of said laser beam are generated at a repetition rate greater than 100 kHz and focused into focal spots having focal spot diameters,

wherein at said repetition rate greater than 100 kHz accumulation of overlapping pulses within said medium and over said focal spot diameters results in improved contrast in said greyscale image while forming an image portion in a shorter time relative to contrast at time obtainable at a repetition rate less than 100 kHz.

2. The method of claim 1, wherein said plurality of pulses is generated at a repetition rate greater than about 10 kHz.

3. The method of claim 1, wherein the pulse width of the optical pulses is less than about 10 picoseconds.

4. The method of claim 1, wherein the optical pulses have an energy in a range from about 100 nJ to about 100 μ

J.

5. The method of claim 1, further comprising receiving an electronic image file comprising information related to an image that is to be substantially replicated as the grayscale image obtainable from the medium.

6. The method of claim 1, wherein varying the optical energy comprises modulating a scan speed of the laser beam relative to the surface.

7. The method of claim 1, wherein varying the optical energy comprises varying overlap of focal spot sizes of the optical pulses at the surface of the medium.

8. The method of claim 1, wherein altering at least one of reflectivity, absorptivity, or diffractive properties comprises altering the reflectivity.

9. The method of claim 1, wherein the grayscale image is obtainable by illuminating the medium with light.

10. A medium modified by the method of claim 1 so that a grayscale image is obtainable from the medium wherein the grayscale image comprises a representation of a person, an animal, a natural structure, a manmade structure, or a work of artistic expression.

11. A system of modifying a medium so that a grayscale image is obtainable from the medium, the system comprising:

a laser source capable of outputting a laser beam comprising a plurality of optical pulses having a pulse width less than about 100 picoseconds, wherein the laser source comprises a fiber laser and further comprises an optical modulator;

a support for holding a medium having a surface;

a scanning system configured to relatively scan the laser beam with respect to the surface of the medium; and

a controller configured to vary optical energy delivered by the laser beam to different regions of the surface of the medium based on a desired grayscale, thereby altering at least one of reflectivity, absorptivity, or diffractivity of the regions to provide the grayscale image obtainable from the medium, said controller configured to generate pulses at a variable repetition rate by controlling said optical modulator, at least some pulses being generated at a repetition rate greater than 100 kHz.

12. The system of claim 11, wherein the laser source further comprises a frequency converter.

13. The system of claim 11, wherein the laser source comprises an oscillator and an amplifier.

14. The system of claim 11, wherein the scanning system is configured to scan the laser beam with respect to the surface of the medium at a first scan speed and at a second scan speed, the second scan speed greater than the first scan speed.

15. A medium modified by the system of claim 11 so that a grayscale image is obtainable from the medium, wherein the grayscale image comprises a representation of a person, an animal, a natural structure, a manmade structure, or a work of artistic expression.

16. A method of modifying a medium having a surface so that a grayscale image is obtainable from the medium, the method comprising:

scanning a first laser beam relative to the surface at a first scan speed, the first laser beam comprising a plurality of first optical pulses having a first pulse width less than about 100 picoseconds, wherein at least a portion of said plurality of first optical pulses of said first laser beam are generated at a repetition rate greater than 100 kHz, the first laser beam delivering first optical energy to an area of the surface of the medium;

varying the first optical energy delivered to different regions of the area by the first laser beam, thereby altering at least one of the reflectivity, absorptivity, or diffractive properties of the regions in the area to provide a first grayscale image obtainable from the medium, the first grayscale image having a first visibility;

scanning a second laser beam relative to the surface at a second scan speed, the second scan speed greater than the first scan speed, the second laser beam comprising a plurality of second optical pulses having a second pulse width less than about 100 picoseconds, wherein at least a portion of said plurality of second optical pulses of said second laser beam are generated at a repetition rate greater than 100 kHz, the second laser beam delivering second optical energy to at least a portion of the area scanned by the first laser beam; and

varying the second optical energy delivered to different regions in the area, thereby providing a second grayscale image obtainable from the medium, the second grayscale image having a second visibility, the second visibility greater than the first visibility.

17. The method of claim 16, wherein the first pulse width is substantially the same as the second pulse width.