Method for determining print parameter values of an inkjet printing device, data processing system, method for inkjet printing and device

Abstract

Method for determining print parameter values of an inkjet printing device, data processing system, method for inkjet printing, and device. There is provided a computer-implemented method (100) for determining print parameter values (1) of an inkjet printing device (2) for printing a pattern on a surface (3) of an ophthalmic lens substrate (4) including a curved surface, the inkjet printing device (2) including a print head (5) as a single component having a plurality of print nozzles (6, 6a, 6b, 6c), the method including the following method steps: grouping the plurality of print nozzles (6, 6a, 6b, 6c) into at least two print nozzle groups (10a, 10b, 10c, 10d, 10e), and individually determining the print parameter values (1) of at least one adjustable print parameter (7, 7a, 7b, 7c, 7d, 7e, 7f) for each print nozzle group (10a, 10b, 10c, 10d, 10e), wherein the print head (5) and the ophthalmic lens substrate (4) are configured not to be tilted.

Description

[0001] This application is a divisional application of the patent application with the filing date of September 9, 2022, application number 202280057751.X, international application number PCT / EP2022 / 075053, and invention title "Computer-implemented method for determining print parameter values of an inkjet printing device, data processing system, method for inkjet printing, and inkjet printing device". Technical Field

[0002] The present invention relates to a computer-implemented method for determining print parameter values of an inkjet printing device (the inkjet printing device includes a print head having a plurality of print nozzles) for printing a pattern on a surface of an ophthalmic lens substrate, a data processing system, a computer program, a non-transitory computer-readable storage medium, a method for inkjet printing, an inkjet printing device, and an ophthalmic lens substrate (a pattern is printed on the surface of the ophthalmic lens substrate). Background Art

[0003] Inkjet technology is used for different purposes in the field of ophthalmic lenses, such as for permanent or temporary marking of lenses as disclosed in WO 2010 / 084272 A1 and WO2014 / 053716 A1.

[0004] DE 10 2007 037 730 A1 discloses a method for producing an ophthalmic lens, in which a first mark and a second mark are respectively provided on, in, or under the surfaces of a first optically effective region and a second optically effective region. The second mark has a predetermined three-dimensional positional relationship with the first mark. Both of these marks can be applied by inkjet printing.

[0005] Moreover, as disclosed in US 2019 / 0 310 492 A1, inkjet printing can be used to apply masking on a partial region of the surface of a coated or uncoated ophthalmic lens. The inkjet printing process disclosed therein is regarded as the closest prior art to the present invention.

[0006] Existing inkjet printers used in the ophthalmic lens industry use "flatbed" print heads, which are optimized for applying target materials to flat surfaces. Therefore, these printers provide good results, especially for flat and low-curvature ophthalmic lenses. During the jetting process, the nozzles are filled and emptied (i.e., the ejection of microdrops) with ink by using shock waves caused by piezoelectric actuation. The nozzles can be finely controlled by applying a certain voltage curve thereto. Typical solid ink printers operate at a jetting frequency of 300 to 1000 dpi and 10 to 50 kHz. Among other things, adjustable parameters also include emission frequency, waveform, norm, and jetting temperature.

[0007] However, when applying inkjet technology to spectacle lenses with a large curvature, the inventors of the present invention recognized a printing quality problem. The inventors found that the printing quality varies in different regions of the lens. For spectacle lenses with a high curvature, the printing quality deteriorates severely towards the edge of the spectacle lens. This is regarded as a direct consequence of the mismatch between the bar-shaped industry printheads of the prior art and the surface of a non-flat (e.g., spherical or freeform) spectacle lens having a dioptric power. For example, the current series of products of the applicant of the present patent application uses blanks with a true front curve radius of 40 mm to 1000 mm.

[0008] WO 03 / 023684A1 relates to the production of three-dimensional decorative objects from a flat substrate. If the substrate is decorated before the production process, during the production process, due to the flow and stretching of the substrate to conform to the shape of the mold or die, the decoration may be misaligned and deformed. If the substrate is decorated after the production process, the distortion of the decoration can be eliminated. However, due to the three-dimensional shape before decoration, the decoration process is complex and costly. The adapted pre-decoration technique employs a deliberately distorted decoration applied to the flat substrate. Since the shape and surface of the substrate change during production, the distorted decoration is intended to transform into its desired appearance. Similar problems are described in the fields of in-mold decoration and insert-mold decoration and in the field of image projection on curved surfaces.

[0009] To solve these problems, WO 03 / 023684A1 proposes a system and method for transforming the appearance of an image with a computer so that the image is adapted to the topography of the substrate to which the image is to be applied. The proposed method includes measuring the topography of the substrate and transforming an untransformed graphic image into a transformed graphic image based on the measured values of the topography of the substrate. However, this method requires a complex determination of the topography of the substrate. Moreover, although WO 03 / 023684A1 mentions that inkjet printing is a suitable method for applying the transformed graphic image to the substrate, the impact of this application method on image distortion is not considered.

[0010] WO 01 / 73492A2 discloses a method for applying lenticular lens technology to a curved surface such that the image distortion experienced by the viewer is small. The method includes preparing an interleaved image for application to the curved surface, the interleaved image consisting of two or more frames such that when the interleaved image is viewed through the lenticular lens from a predetermined viewing distance, the interleaved image is substantially free of distortion. The interleaved image can be printed by inkjet printing. However, the impact of the inkjet printing method on image distortion is not discussed.

[0011] WO 2018 / 197003 A1 discloses a system and method for coating a lens using a plurality of inkjet printheads arranged online. Based on the image to be printed on the lens, a plurality of image layers are generated based on the lens geometry, the target product, and the number of printheads. At least two of the plurality of inkjet printheads are used to print an image on the lens such that each of the at least two printheads can print at least one of the plurality of image layers. To print the image, several printings associated with the movement of the printhead and / or the lens are required. Therefore, a suitable hardware arrangement for the movement is needed, and the whole process can be time-consuming.

[0012] EP 2555043 A1 discloses a method for inkjet printing spectacle lenses with markings. Different values of printing parameters are selected, especially depending on the surface properties of the lens, such as the properties of the coating applied thereto. Thus, each lens is individualized, but each lens is coated with the same parameter values for each printing nozzle. Therefore, due to the curvature of the lens, the printing result may not be satisfactory.

[0013] WO 2020 / 079624 A1 discloses a method for positioning a glass holder during movement and a method for printing an image on the glass holder, which includes the positioning method. Summary of the Invention

[0014] Regarding the above prior art, an object of the present invention is to provide a method that allows inkjet printing of a printed pattern on the surface (such as a curved surface) of a spectacle lens substrate, the printed pattern having enhanced properties.

[0015] Another object of the present invention is to provide a data processing system, a method for inkjet printing, and an inkjet printing device that can achieve better printing results on the surface of a spectacle lens substrate, especially a curved surface.

[0016] The first object is achieved by a computer-implemented method for determining values of printing parameters as described in claims 1 and 20. Another object is achieved by a data processing system as described in claims 11 and 32, a method for inkjet printing as described in claims 15 and 35, and an inkjet printing device as described in claims 17 and 37. The dependent claims contain further developments of the present invention.

[0017] Throughout this specification, the following definitions apply:

[0018] The term "adjustable ink properties" refers to ink properties that can in principle be adjusted by the user, such as ink temperature, ink solids content, etc.

[0019] The term "analysis data" refers to data obtained by analyzing a printed pattern, for example, by an optical microscope or a white light interferometer.

[0020] The term "arc length" refers to the distance between two points on the surface of an ophthalmic lens substrate measured along the surface of the substrate (see Figure 4 ).

[0021] If the surface is part of a rotational surface with continuously variable curvature over all or part of it, the surface is called "aspherical" (ISO 13666:2019(E), section 3.4.3).

[0022] The term "computer" refers to a functional unit that can perform a large number of calculations (including a large number of arithmetic and logical operations) without human intervention. A computer can consist of an independent unit or several interconnected units (ISO / IEC 2382:2015).

[0023] The term "computer-implemented" is an expression intended to cover claims involving a computer, a computer network, or other programmable devices, where at least one feature is implemented by means of a computer program. For example, a computer-implemented method is a method actually executed on a computer.

[0024] The term "computer program" refers to a sequence of computer-executable instructions that specify a method. A computer program is a syntactic unit that conforms to the rules of a specific programming language and consists of declarations, statements, or instructions required to solve a certain function, task, or problem (ISO / IEC 2382:2015).

[0025] The term "cost function" refers to a multi-dimensional mathematical function that defines the cost of a set of printed parameter values corresponding to a specific set of points on the surface of an ophthalmic lens substrate. A path in the cost function that defines a low cost or even the minimum cost is used to derive the parameter mapping. The cost can be defined as one or more quality parameters, for example, the better the quality parameter, the lower the cost. Depending on the specific application, the weights of different quality parameters in the cost function can be changed, that is, one or more specific quality parameters can be emphasized by assigning a higher weight than other quality parameters.

[0026] The term "curved surface" refers to a surface that is not flat and exhibits a concave cross-section or a convex cross-section or both.

[0027] The term "data" refers to a representation of information that can be reinterpreted in a formalized manner suitable for communication, interpretation, or processing (ISO / IEC 2382:2015).

[0028] The term "data processing" refers to the systematic manipulation of data, such as performing arithmetic or logical operations on data, data merging or sorting, program assembly or compilation, or operations on text such as editing, sorting, merging, storing, retrieving, displaying, or printing (ISO / IEC 2382:2015).

[0029] The term "data processing system" refers to one or more computers, peripheral devices, and software that perform data processing (ISO / IEC 2382:2015).

[0030] The term "displacement vector" refers to a geometric object that has a magnitude or length and a direction respectively and describes the relative position of the spectacle lens substrate and the print head with respect to each other, and may refer to a certain reference point.

[0031] The term "distance" refers to the spatial length between two points. Unless otherwise specified, it refers to the length of the shortest straight line between two points.

[0032] The term "jetting temperature" refers to a printing parameter that describes the temperature at the tip of the printing nozzle.

[0033] The term "ambient conditions" refers to the ambient conditions of the spectacle lens substrate and the inkjet printing device used to print a pattern on the surface of the spectacle lens substrate, such as ambient temperature, ambient humidity, etc.

[0034] "Freeform surface" should be understood as a complex surface that can be represented, in particular, by a regionally defined function, especially a regionally defined function that is twice continuously differentiable. Examples of suitable regionally defined functions are (especially piecewise) polynomial functions (especially polynomial splines, such as bicubic splines, higher-order splines of fourth order or higher, non-uniform rational polynomial B-splines (NURBS)). In contrast, simple surfaces, such as spherical surfaces, aspherical surfaces, cylindrical surfaces, and toric surfaces, which are described as circular along at least one principal meridian. In particular, freeform surfaces do not need to exhibit axial symmetry or point symmetry and can have different values for the mean surface refractive index in different regions of the surface. According to ISO 13666:2019(E), section 3.7.7, spectacle lenses exhibiting freeform surfaces can be considered varifocal lenses, i.e., spectacle lenses having a smooth variation of focusing power over part or all of their area, with discontinuities, designed to provide more than one focusing power.

[0035] The term "geometric features" refers to the geometric properties of the spectacle lens substrate, such as its dimensions, its surface curvature, etc., and the geometric properties of the print head, such as its dimensions, orientation, the pitch of individual nozzles, the arrangement of nozzles, etc. For example, surface curvature can be described by a surface sag function.

[0036] The term "geometric relationship" refers to the alignment of the print head and the spectacle lens substrate relative to each other. For example, this geometric relationship can be described by a displacement vector, a velocity vector, an incident angle α, a distance, or an arc length s.

[0037] The term "gray level" refers to the number of droplet sizes that a nozzle can produce, including the "empty droplet" when no droplet is ejected.

[0038] The term "incident angle" refers to the angle α between the normal vector n at a point on the surface of the spectacle lens substrate and the ejection vector j, at which the ejected ink is transferred from the nozzle to the lens surface (see Figure 4 ).

[0039] The term "ink" refers to any component that can be deposited droplet by droplet during an inkjet printing process, regardless of its color ("material to be ejected"). To enable or facilitate the formation and deposition of droplets, it may be necessary to heat the ink to a certain temperature.

[0040] The term "inkjet printing" refers to drop-on-demand inkjet printing, which is a non-contact method of forming a pattern on a surface by the discrete deposition of ink droplets. Inkjet printing is performed by an inkjet printing device, which includes a print head having a plurality of printing nozzles.

[0041] The term "input data" refers to data to be stored or processed in an input data processing system or any of its parts. Input data can also refer to data that any component of a computer is receiving or will receive (ISO / IEC 2382:2015).

[0042] The term "instruction" refers to an operation description and the identification of any associated operands (ISO / IEC 2382:2015).

[0043] The term "inkjet duration" refers to a printing parameter that describes the time period during which ink is ejected from a certain printing nozzle.

[0044] The term "ejection frequency" refers to a printing parameter that describes the amount of ejection events of a certain printing nozzle in each time period (such as per second or per minute). The general ejection frequency is in the kilohertz range, for example, between 10 kHz and 50 kHz.

[0045] The term "look-up table" refers to a data array that associates different parameters (such as parameters that describe the geometric relationship between the surface of the spectacle lens substrate and the print head) with adjustable printing parameters. If necessary, the look-up table can be stored and used for parameter mapping.

[0046] The term "material property" refers respectively to the properties of the ink and / or the properties of the spectacle lens substrate and its surface. Examples of ink material properties are: static and dynamic viscosity, static and dynamic surface tension, charge, etc. Examples of material properties of the spectacle lens substrate and its surface are: surface hydrophobicity, surface charge, surface treatment, surface function, etc.

[0047] The term "non-adjustable ink property" refers to an ink property that cannot be adjusted by the user, such as the chemical composition of the ink.

[0048] The term "non-transitory computer-readable storage medium" refers to a storage medium for permanently storing data, i.e., it can store data even without electricity. Examples include flash memory, read-only memory, ferroelectric random access memory, most types of magnetic computer storage devices (such as hard disk drives, floppy disks, and magnetic tapes), and optical discs.

[0049] The term "scaling value" refers to a printing parameter that describes a multiplicative variable coefficient by which the voltage applied to a certain printing nozzle is adjusted. Adjustment of the scaling value is used to calibrate the emission signal of the print head. The scaling value can be regarded as a variable coefficient that quantifies the change in emission voltage for each nozzle.

[0050] The term "optimization" refers to a process aimed at achieving the optimal value of one or more properties. For example, optimizing a parameter map means improving the parameter map with respect to a certain property or target value.

[0051] The term "pattern" refers to one or more macroscopic elements, such as numbers, letters of any type of graphic, graphic representations such as dots, symbols, etc.

[0052] The term "parameter" refers to a variable that describes a certain property of an object or method, where the property is, for example, temperature, distance, ejection frequency, etc. Each parameter exhibits a certain "parameter value", which can be constant or variable, such as 25 °C, 10 mm, 20 kHz, etc.

[0053] The term "parameter map" refers to the assignment of different printing parameter values (such as P(x, y, z)) to a set of specific points (x, y, z) on the surface of the spectacle lens substrate. These sets of points can be defined by having similar "cost values", which are determined according to a cost function and the surface geometry as input. The parameter map for each surface can be unique. The process for obtaining such a parameter map is called parameter mapping. For example, dividing an image into, for example, 8 sub-images using these specific sets of points can be understood as parameter mapping, where these sub-images are printed with 8 sets of different printing parameter values P.

[0054] The term "pose" is understood to mean the combination of the position and orientation of a named object or component (such as a spectacle lens substrate or a print head) or a reference axis in three-dimensional space. See also ISO 8373:2021-11, section 5.5. Accordingly, the position of a point mass relative to a Cartesian coordinate system is defined by the distances along the coordinate directions x, y, z. If a second Cartesian coordinate system is spanned at this mass point, the orientation of this coordinate intersection is defined by the angular offsets of its coordinate axes relative to the corresponding axes of the base coordinate system. Three additional angles are required to describe the position of the new coordinate system relative to the base coordinate system.

[0055] The term "print head" refers to the part of an inkjet printing device that carries the printing nozzles. Preferably a single component . The print head may allow complete coverage of the surface to be printed, i.e., the entire surface to be printed can be printed in a single pass using a single print head.

[0056] The term "printing nozzle" refers to the nozzle of an inkjet printing device. A plurality of printing nozzles are arranged on the print head of the inkjet printing device. During the ink jetting process, the nozzles are filled and emptied of ink by using shock waves caused by piezoelectric actuation. Therefore, a certain voltage curve is applied to the printing nozzles.

[0057] The term "printing nozzle group" refers to one or more printing nozzles that are commonly controlled using the same printing parameter values. A printing nozzle group may only cover a part of the surface to be printed in a single pass, i.e., it may be necessary to use the printing nozzles of at least two printing nozzle groups to print on the entire surface to be printed.

[0058] The term "printing parameter" refers to the parameters of the printing process. Printing parameters can be either adjustable printing parameters, i.e., printing parameters that the user can, in principle, adjust, such as jetting frequency, jetting temperature, jetting duration; or non-adjustable printing parameters, i.e., printing parameters that the user cannot adjust, such as the geometry of the print head, the quantity of printing nozzles. A number of printing parameters can be combined into a so-called gray level. That is, in the present disclosure, the gray level can be regarded as a common printing parameter rather than a number of printing parameters.

[0059] The term "printing parameter value" refers to the parameter value of a printing parameter.

[0060] The term "printing process" refers to an inkjet printing process using drop-on-demand technology, i.e., a process for depositing ink droplets on the surface of a substrate. The printing process can be described by printing parameters and their corresponding printing parameter values.

[0061] The term "processor" refers to the functional unit in a computer that interprets and executes instructions. The processor may be part of a processing unit, which is a functional unit consisting of one or more processors and their internal memories (ISO / IEC 2382:2015).

[0062] The term "quality parameter" refers to a parameter that describes the quality of an inkjet printing process, such as the number of satellites, the roundness of the printed features, etc.

[0063] The term "single-pass printing" refers to a printing process in which the printing nozzles of at least two printing nozzle groups are simultaneously used to print a pattern on the surface of an ophthalmic lens substrate. In other words, at least two printing nozzle groups are to be used within the same printing. One printing may correspond to one printing layer or image layer, that is, at least two printing nozzle groups may be used to print a single printing layer or image layer.

[0064] The term "ophthalmic lens" refers to an ophthalmic lens that is worn in front of the eyeball but does not contact the eyeball (ISO13666:2019(E), section 3.5.2), where an ophthalmic lens is a lens intended for measuring, correcting, and / or protecting the eye, or changing its appearance (ISO 13666:2019(E), section 3.5.1).

[0065] The term "ophthalmic lens substrate" refers to a piece of optical material used in the manufacture of an ophthalmic lens, such as the precursor of a finished ophthalmic lens and the finished lens itself (ISO 13666:2019(E), section 3.8.9). The precursor of a finished lens is, for example, a lens blank, where the term "lens blank" refers to a piece of optical material having one optically finished surface for making a lens (ISO 13666:2019(E), section 3.8.1), or an uncut finished lens, where the term "uncut finished lens" describes the finished lens before edging (ISO 13666:2019(E), section 3.8.8).

[0066] If the surface is part of the inner or outer surface of a sphere (ISO 13666:2019(E), section 3.4.1) such that its cross-section is circular in every meridian, the surface is called "spherical".

[0067] The term "storage medium" refers to a functional unit in which data can be placed, data can be stored, and data can be retrieved (ISO / IEC 2382:2015).

[0068] The term "surface" refers to any layer of a three-dimensional spectacle lens substrate or a three-dimensionally coated lens that is in direct contact with the environment. This surface can be regarded as its boundary. The surfaces of a spectacle lens substrate include its front surface (ISO 13666:2019(E), section 3.2.13), edge, and rear surface (ISO 13666:2019(E), section 3.2.14). Examples of different shaped surfaces (surface types) include freeform progressive surfaces, freeform single vision surfaces, surfaces with a changing dioptric power, (a) spherical surfaces, cylindrical surfaces, and (a) toric surface. However, the present invention is not limited to a certain surface type.

[0069] In the context of a spectacle lens, the expression "front surface" is used for the surface of a spectacle lens that is intended to be fitted away from the eye (ISO 13666:2019(E), section 3.8.13). In the context of a lens blank, the expression "front surface" is used for the surface that will ultimately become the front surface of the spectacle lens manufactured from the lens blank. The curvature of a section of the front surface of a lens blank, which is used as the starting object for manufacturing a spectacle lens, may already be similar to the curvature of the spectacle lens to be manufactured.

[0070] In the context of a spectacle lens, the expression "rear surface" is used for the surface of a spectacle lens that is intended to be fitted close to the eye (ISO 13666:2019(E), section 3.8.14). In the context of a lens blank, the expression "rear surface" is used for the surface that will ultimately become the rear surface of the spectacle lens manufactured from the lens blank. The rear surface of a semi-finished lens blank can be machined during the manufacturing process of a spectacle lens.

[0071] The term "velocity vector" refers to a geometric object that has a magnitude or length and a direction respectively and describes the relative movement speed of a spectacle lens substrate and a print head with respect to each other, and may refer to a certain reference point.

[0072] The term "virtual representation of a device" refers to a digital representation of a device (so-called digital twin), such as an implementation of a device with corresponding structural design features and / or a digital and / or analytical data set (digital and / or analytical representation) that describes the design features. For example, such a data set can be stored in the memory of a computer or on a computer-readable (especially non-transitory) storage medium. Additionally, the data set can be retrieved from a data network, for example, retrieved from the Internet or a local area network (LAN). A data set similar to the representation of a device can include various features of the device, especially descriptions of structural features, unit materials, etc. For example, such a description can include a mathematical description of the structural features of the device. The virtual representation can be in an encoded or encrypted form. Additionally or alternatively, the virtual representation of a device can also include computer-readable instructions for controlling one or more manufacturing machines of the device in order to produce a physical device with corresponding features.

[0073] The term "waveform parameter" refers to a printing parameter that describes the voltage curve applied to a printing nozzle, such as the minimum voltage, maximum voltage, slope, duration of the applied voltage, etc. Generally, the voltage curve is described by a plurality of waveform parameters. In the context of the present invention, one or more waveform parameters can be adjusted.

[0074] As used in this specification and the appended claims, the articles "a", "an", and "the" include plural referents unless expressly and unambiguously limited to one referent.

[0075] When used in a series of two or more elements, the term "and / or" as used herein means that any of the listed elements can be used alone, or any combination of two or more of the listed elements can be used. For example, when describing the use of methods A, B, and / or C, method A alone can be used; B alone; C alone; A and B together; A and C together; B and C together; or A, B, and C together.

[0076] In a first aspect, the present invention provides a computer-implemented method for determining the values of printing parameters of an inkjet printing device for printing a pattern on the surface, in particular on a curved surface, of an ophthalmic lens substrate. The inkjet printing device includes a printhead having a plurality of printing nozzles.

[0077] According to the present invention, the method includes the following method steps: grouping a plurality of printing nozzles into at least two printing nozzle groups, and separately determining (e.g., calculating) the values of the printing parameters of at least one adjustable printing parameter for each printing nozzle group. Preferably, at least two printing nozzle groups are to be used within a single pass of printing.

[0078] The surface of the ophthalmic lens substrate can be the front surface or the back surface. In addition, the surface can also be a spherical surface, an aspherical surface, a freeform surface, or any other surface type, such as one of those mentioned above. The surface types of the front surface and the back surface can be the same or different from each other.

[0079] One printing nozzle group can include a single (i.e., only one) printing nozzle, several printing nozzles, or a plurality of printing nozzles. The amount of printing nozzle groups can vary between at least two printing nozzle groups and the number of printing nozzle groups equal to the number of printing nozzles (i.e., each printing nozzle group may include only a single printing nozzle). The smaller the amount of printing nozzle groups, the easier it is to determine and optimize the corresponding printing parameter values. As the amount of printing nozzle groups increases, the printing parameter values can be better adapted to the surface of the ophthalmic lens substrate, and better printing results can be obtained.

[0080] A basic concept of the present invention is based on the following discovery: By optimizing the printing parameter values of a set of printing nozzles or even each individual printing nozzle, the overall printing quality that can be measured by parameters such as dot shape and impact area can be significantly improved. In particular, the printing parameter values can be determined and optimized individually for different relative positions between the print head and the spectacle lens substrate. Other or additional influencing factors that may affect the printing result can also be considered, such as anisotropic surface structures or surface hydrophobicity.

[0081] Moreover, the proposed method allows for obtaining an improved printing pattern in a single pass of printing. In other words, there is no need to print different layers, which saves time and production costs. In addition, only one print head is required, which further saves time and production costs. The hardware arrangement for moving the spectacle lens substrate and / or the print head can be omitted.

[0082] The proposed method can be used in any process for constructing, coating, and / or modifying the surface or within the material of a spectacle lens substrate using inkjet printing technology, such as coloring using coating or diffusion procedures, permanent or temporary marking of lenses, masking layers, adhesive layer dots, additive manufacturing, etc. This procedure is particularly suitable for the processing of spectacle lens substrates, the printing results of which can be optimized "by software" (i.e., by the computer-implemented method of the present invention), rather than introducing complex positioning systems or robots to compensate for the general settings of printing parameters. Since the surface of a spectacle lens substrate usually has a unique shape, for example due to customization requirements, the proposed method enables fast printing with high-quality printing and low equipment expenditure. The described method expands the range of spectacle lens substrates that can be printed with high quality and, therefore, enables the further application of inkjet printing technology to the production of spectacle lenses.

[0083] At least one adjustable printing parameter can be selected from the group consisting of ejection temperature, ejection duration, ejection frequency, fan value, waveform parameter, and adjustable ink properties. Preferably, the printing parameter values of more than one printing parameter are determined individually (i.e., for each printing nozzle group). The fewer the printing parameters considered and the amount of corresponding printing parameter values to be determined, the easier their determination and possible optimization will be. As the amount of printing parameter values to be determined increases, the printing process can be better adapted to the surface of the spectacle lens substrate, and better printing results can be obtained.

[0084] For example, the control jetting frequency can set the arrival time interval, i.e., the duration between adjacent droplets. For a high jetting frequency, the arrival time interval between adjacent droplets is less than the solidification time of the droplets. In contrast, at a low jetting frequency, the arrival time interval between adjacent droplets is greater than the solidification time of the droplets. This results in no coalescence between adjacent droplets. The printing parameter values adapted based on the geometric characteristics of the spectacle lens substrate and the print head result in a higher printing quality, fewer satellites around the droplets, and less distortion of the droplet shape.

[0085] In a specific development of the method according to the invention, the method can include obtaining input data related to the surface of the spectacle lens substrate and the geometric characteristics of the print head. Then, depending on the input data, i.e., the surface of the spectacle lens substrate and the geometric characteristics of the print head, the printing parameter values can be determined individually. Analyzing the surface of the spectacle lens substrate to be printed and the geometric characteristics of the print head, especially the surface curvature, allows the derivation of the geometric relationship between the spectacle lens substrate and the print head during the printing process. In other words, the input data can be used to determine the geometric relationship between the surface of the spectacle lens substrate and the print head, where the geometric relationship is described by at least one parameter selected from the group consisting of a displacement vector, a velocity vector, an incident angle α, a distance, or an arc length s. At least one parameter, preferably more than one parameter, or even all parameters can be selected and used to individually determine the printing parameter values.

[0086] Taking into account this geometric relationship, for each nozzle or nozzle group of the print head, the individual fine-grained and optimized printing parameter values of at least one printing parameter can be determined (e.g., calculated). In other words, the printing parameter values can be determined with respect to the geometric characteristics, which allows the improvement of the printing quality on the curved surface by individually controlling each print nozzle group. There is no need for a complex positioning system or a robot to compensate for the general setting of the printing parameters by positioning the spectacle lens substrate and the print head relative to each other. In addition, a print head with a non-flat surface (i.e., the plane on which the print nozzles are arranged) can be conveniently used.

[0087] For example, the input data can be obtained by receiving input data via wired or wireless transmission from a storage unit for storing the geometric characteristics of different spectacle lens substrates and / or print heads. Other possible ways are to manually or automatically input the geometric characteristics using an input unit coupled to the data processing system that executes the method according to the invention. The geometric characteristics can be provided, for example, in the form of tabular values, or the geometric characteristics can be directly measured and processed using a suitable measuring system. A combination is also possible.

[0088] In addition to the geometric characteristics of the spectacle lens substrate and the print head, the input data can also include data related to environmental conditions, non-adjustable ink characteristics, and / or the material characteristics of the spectacle lens substrate.

[0089] By taking these additional influencing factors into account when determining the printing parameter values, the printing process can be better adapted to the overall conditions and the printing result can be further improved. For example, when deriving at least one of the parameter mappings described below, these additional influencing factors can be considered, that is, the parameter mapping not only describes the geometric relationship between the spectacle lens substrate and the print head during the printing process, but also includes other influencing factors that may affect the printing process.

[0090] In a further specific development of the method according to the invention, the method step of separately determining the printing parameter value of at least one adjustable printing parameter may include deriving a parameter mapping that includes assigning a printing parameter value to a specific set of points on the surface of the spectacle lens substrate.

[0091] To derive the parameter mapping, known geometric features (e.g., as part of the input data, describing the surface of the spectacle lens substrate, such as the true front curve radius) can be used to transform the surface into a grid or mesh of data points. Then, these data points can be looped through and the working settings (i.e., a set of printing parameter values) can be looked up in a previously created general lookup table. This lookup table can include optimized printing parameter values for certain data points and a certain print head (i.e., a certain geometric relationship between the spectacle lens substrate and the print head). The same data point stored in this lookup table can exist on many different surfaces.

[0092] The derived parameter mapping can form a basic reference system to optimize the entire printing parameter space as a function of the angle of incidence, the nozzle-to-substrate distance, the velocity vector of the print head, the ejection frequency, and the ejection duration, for example, to optimize the dot shape or weight of the ink droplets.

[0093] For example, the parameter mapping can be derived by optimizing a cost function that is applied to the correlation between the parameters describing the geometric relationship between the surface of the spectacle lens substrate and the print head and the printing parameter values of the adjustable printing parameters, for example, the correlation stored in the lookup table.

[0094] The optimization of the cost function can be accomplished by using at least one method that can be selected from the group consisting of the steepest gradient descent method, genetic algorithms, and machine learning. For example, the so-called Broyden-Fletcher-Goldfarb-Shanno algorithm can be used for optimization.

[0095] In addition, machine learning processes can also be used for optimization. This can detect and take into account other influencing factors whose effects have not yet been considered.

[0096] In a further specific development of the method according to the invention, the printing parameter values of at least one adjustable printing parameter of each printing nozzle group can be determined individually, such that it is not necessary to adjust the inclination angle of the print head relative to the surface of the spectacle lens substrate before and / or during printing.

[0097] For example, during the entire printing process, the surface to be printed and the surface of the print head including the printing nozzles can be oriented substantially parallel.

[0098] This avoids complex hardware arrangements for rotating (e.g., mechanically tilting) the spectacle lens substrate and / or the print head before and / or during printing, which would otherwise be required to optimize the printing result. Only via fully personalized printing parameter values, i.e., personalized ejection profiles of the printing nozzle groups, can the effects achieved by complex hardware arrangements (such as tilting devices) in the prior art be mimicked.

[0099] Depending on the size of the print head and the surface to be printed, i.e., in the case where the size of the print head allows covering the entire surface to be printed, during printing a pattern on the surface of the spectacle lens substrate, the postures (i.e., positions and orientations) of both the spectacle lens substrate and the print head can even remain unchanged relative to each other. In other words, without moving the spectacle lens substrate and the print head relative to each other, an improved pattern can be obtained merely by adjusting the printing parameter values of one or more adjustable printing parameters. This can allow for a more simplified hardware arrangement.

[0100] According to another aspect of the invention, there is provided a data processing system comprising a processor and a storage medium coupled to the processor. The processor is adapted to determine the printing parameter values of an inkjet printing device based on a computer program stored on the storage medium, the inkjet printing device including a print head having a plurality of printing nozzles for printing a pattern on the surface of a spectacle lens substrate.

[0101] The processor is adapted to group the plurality of printing nozzles into at least two printing nozzle groups and individually determine the printing parameter values of at least one adjustable printing parameter of each printing nozzle group. Preferably, at least two printing nozzle groups are to be used within a single pass of printing.

[0102] In other words, the data processing system is configured to execute one of the computer-implemented methods described above for determining the printing parameter values of an inkjet printing device for printing a pattern on the surface of a spectacle lens substrate. Accordingly, the description of the computer-implemented method for determining the printing parameter values of an inkjet printing device for printing a pattern on the surface of a spectacle lens substrate and its advantages is referred to above.

[0103] In a specific development, the processor is adapted to individually determine the printing parameter values depending on the geometric characteristics of the spectacle lens substrate and the print head.

[0104] According to another aspect of the present invention, there is provided a computer program comprising instructions which, when executed by a computer, cause the computer to determine print parameter values for an inkjet printing device for printing a pattern on the surface of a spectacle lens substrate, the inkjet printing device comprising a print head having a plurality of print nozzles. The instructions cause the computer to group the plurality of print nozzles into at least two print nozzle groups and separately determine the print parameter values of at least one adjustable print parameter for each print nozzle group. Preferably, at least two print nozzle groups are to be used within a single pass of printing.

[0105] In other words, the computer program comprises instructions for performing one of the computer-implemented methods for determining print parameter values for an inkjet printing device for printing a pattern on the surface of a spectacle lens substrate as described above. Thus, the description of the computer-implemented method for determining print parameter values for an inkjet printing device for printing a pattern on the surface of a spectacle lens substrate and its advantages is referred to above.

[0106] According to another aspect of the present invention, there is provided a non-transitory computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to determine print parameter values for an inkjet printing device for printing a pattern on the surface of a spectacle lens substrate, the inkjet printing device comprising a print head having a plurality of print nozzles. The instructions cause the computer to group the plurality of print nozzles into at least two print nozzle groups and separately determine the print parameter values of at least one adjustable print parameter for each print nozzle group. Preferably, at least two print nozzle groups are to be used within a single pass of printing.

[0107] In other words, the non-transitory computer-readable storage medium comprises instructions for performing one of the computer-implemented methods for determining print parameter values for an inkjet printing device for printing a pattern on the surface of a spectacle lens substrate as described above. Thus, the description of the computer-implemented method for determining print parameter values for an inkjet printing device for printing a pattern on the surface of a spectacle lens substrate and its advantages is referred to above.

[0108] According to another aspect of the present invention, there is provided a method for inkjet printing, wherein a pattern is printed on the surface of a spectacle lens substrate using an inkjet printing device comprising a print head having a plurality of print nozzles with print parameter values of at least one adjustable print parameter. The print parameter values of the at least one adjustable print parameter are determined according to the computer-implemented method as described above.

[0109] In other words, after determining the printing parameter values of at least one adjustable printing parameter by a computer-implemented method for determining the printing parameter values of an inkjet printing device for printing a pattern on the surface of an ophthalmic lens substrate, the inkjet printing device includes a print head having a plurality of printing nozzles, wherein the method includes: grouping the plurality of printing nozzles into printing nozzle groups and separately determining the printing parameter values of at least one adjustable printing parameter for each printing nozzle group, and the actual printing can be performed using the determined printing parameter values. Thus, a description of a computer-implemented method for determining the printing parameter values of an inkjet printing device for printing a pattern on the surface of an ophthalmic lens substrate and its advantages is described above. For example, the inkjet printing method can be used for coloring using a coating or diffusion process, permanent or temporary marking of the lens, masking layer, adhesive layer points (e.g., increasing surface roughness for coating), additive manufacturing, etc.

[0110] In a specific development of the inkjet printing method, the inclination angle of the print head relative to the surface of the ophthalmic lens substrate is not adjusted before and / or during printing.

[0111] For example, throughout the printing process, the surface to be printed and the surface of the print head including the printing nozzles can be oriented substantially parallel.

[0112] This avoids a complex hardware arrangement for rotating (e.g., mechanically tilting) the ophthalmic lens substrate and / or the print head before and / or during printing, which would otherwise be required to optimize the printing result. Only via fully personalized printing parameter values, i.e., the personalized ejection profiles of the printing nozzle groups, can the effects achieved by complex hardware arrangements (such as tilting devices) in the prior art be mimicked.

[0113] Depending on the size of the print head and the surface to be printed, i.e., in the case where the size of the print head allows covering the entire surface to be printed, during printing a pattern on the surface of the spectacle lens substrate, the postures (i.e., positions and orientations) of both the spectacle lens substrate and the print head can even remain unchanged relative to each other. In other words, without moving the spectacle lens substrate and the print head relative to each other, by merely adjusting the print parameter values of one or more adjustable print parameters, an improved pattern can be obtained. This can allow for a more simplified hardware arrangement. According to another aspect of the present invention, there is provided an inkjet printing device for printing a pattern on the surface of a spectacle lens substrate. The inkjet printing device includes a print head having a plurality of print nozzles and a data processing system, the data processing system including a processor and a storage medium coupled to the processor, wherein the processor is adapted to determine the print parameter values based on a computer program stored on the storage medium. The processor is adapted to group the plurality of print nozzles into at least two print nozzle groups and separately determine the print parameter values of at least one adjustable print parameter for each print nozzle group. Preferably, at least two print nozzle groups are to be used within a single pass of printing.

[0114] The inkjet printing device is configured to perform the method for inkjet printing as described above. Thus, reference is made to the description above of the method for inkjet printing (wherein a pattern is printed on the surface of the spectacle lens substrate) and its advantages.

[0115] According to another aspect of the present invention, there is provided a data set in the form of a computer-readable data signal, the data set including at least one of the following types of data: (i) a virtual representation of the inkjet printing device as described above, the virtual representation being configured to be fed into one or more manufacturing machines to manufacture the device, or (ii) data containing computer-readable instructions for controlling one or more manufacturing machines to manufacture the inkjet printing device as described above.

[0116] According to another aspect of the present invention, there is provided a data set in the form of a computer-readable data carrier signal. The data set includes at least one of the following types of data: (i) separate print parameter values of at least one adjustable print parameter for at least two print nozzle groups of an inkjet printing device including a print head having a plurality of print nozzles, the print parameter values being configured to be fed into the inkjet printing device to print a pattern on the surface of the spectacle lens substrate; or (ii) data containing computer-readable instructions for controlling the inkjet printing device to print a pattern on the surface of the spectacle lens substrate by applying the separate print parameter values of at least one adjustable print parameter to at least two print nozzle groups of an inkjet printing device including a print head having a plurality of print nozzles.

[0117] The data set can be used to perform the method for inkjet printing as described above, i.e., a method of printing a pattern on the surface of an ophthalmic lens substrate using a value of a printing parameter of at least one adjustable printing parameter with an inkjet printing device including a print head having a plurality of printing nozzles.

[0118] The data can be obtained by performing a computer-implemented method for determining a value of a printing parameter of an inkjet printing device for printing a pattern on the surface of an ophthalmic lens substrate as described above. Thus, reference is made to the description of this method and its advantages above.

[0119] According to another aspect of the present invention, there is provided a computer-implemented method for determining a value of a printing parameter of an inkjet printing device for printing a pattern on a curved surface of an ophthalmic lens substrate, the inkjet printing device including a print head having a plurality of printing nozzles. The method includes the following method steps: obtaining input data related to the surface of the ophthalmic lens substrate and the geometric features of the print head, wherein the input data is used to determine the geometric relationship between the surface of the ophthalmic lens substrate and the print head; grouping the plurality of printing nozzles into at least two printing nozzle groups, and separately determining a value of at least one adjustable printing parameter for each printing nozzle group depending on the geometric relationship. Preferably, at least two printing nozzle groups are to be used in a single pass printing.

[0120] The surface of the ophthalmic lens substrate can be a front surface or a rear surface. In addition, the surface can also be a spherical surface, an aspherical surface, a freeform surface or any other surface type, such as one of those mentioned above. The surface types of the front surface and the rear surface can be the same or different from each other.

[0121] A printing nozzle group can include a single (i.e., only one) printing nozzle, several printing nozzles or a plurality of printing nozzles. The amount of printing nozzle groups can vary between at least two printing nozzle groups and the number of printing nozzle groups equal to the number of printing nozzles (i.e., each printing nozzle group can include only a single printing nozzle). The smaller the amount of printing nozzle groups, the easier it is to determine and optimize the corresponding printing parameter value. As the amount of printing nozzle groups increases, the printing parameter value can be better adapted to the surface of the ophthalmic lens substrate, and better printing results can be obtained.

[0122] A basic concept of the present invention is based on the following discovery: By optimizing the printing parameter values of a set of printing nozzles or even each individual printing nozzle, the overall printing quality measured by parameters such as dot shape and impact area can be greatly improved. In particular, the printing parameter values can be determined and optimized individually for different relative positions between the print head and the spectacle lens substrate. Other or additional influencing factors that may affect the printing result can also be considered, such as anisotropic surface structures or surface hydrophobicity. In addition, a print head with a non-flat surface (i.e., the plane on which the printing nozzles are arranged) can be conveniently used.

[0123] Moreover, the proposed method allows for an improved printing pattern to be obtained in a single pass of printing. In other words, there is no need to print different layers, which saves time and production costs. In addition, only one print head is required, which further saves time and production costs. The hardware arrangement for moving the spectacle lens substrate and / or the print head can be omitted.

[0124] The proposed method can be used in any process for constructing, coating, and / or modifying the surface and / or material within the spectacle lens substrate using inkjet printing technology, such as coloring using a coating or diffusion process, permanent or temporary marking of the lens, masking layer, adhesive layer dots, additive manufacturing, etc. This procedure is particularly suitable for the processing of spectacle lens substrates, whose printing results can be optimized "by software" (i.e., by the computer-implemented method of the present invention), rather than introducing complex positioning systems or robots to compensate for the general settings of the printing parameters. Since the surface of the spectacle lens substrate usually has a unique shape, for example due to customization requirements, the proposed method enables fast printing with high-quality printing and low equipment expenditure. The described method extends the range of spectacle lens substrates that can be printed with high quality and thus enables the further application of inkjet printing technology in the production of spectacle lenses.

[0125] At least one adjustable printing parameter can be selected from the group consisting of jetting temperature, jetting duration, jetting frequency, fan value, waveform parameter, and adjustable ink properties. Preferably, the printing parameter values of more than one printing parameter are determined individually (i.e., for each group of printing nozzles). The fewer the printing parameters considered and the corresponding printing parameter values to be determined, the easier their determination and possible optimization will be. As the amount of printing parameter values to be determined increases, the printing process can be better adapted to the surface of the spectacle lens substrate, and better printing results can be obtained.

[0126] For example, controlling the ejection frequency can set the arrival time interval, i.e., the duration between adjacent droplets. For a high ejection frequency, the arrival time interval between adjacent droplets is less than the solidification time of the droplets. Conversely, at a low ejection frequency, the arrival time interval between adjacent droplets is greater than the solidification time of the droplets. This results in no coalescence between adjacent droplets. Printing parameter values adapted based on the geometric characteristics of the spectacle lens substrate and the print head result in higher printing quality, fewer satellites around the droplets, and less distortion of the droplet shape.

[0127] Analyzing the surface of the spectacle lens substrate to be printed and the geometric characteristics of the print head, especially the surface curvature, allows the derivation of the geometric relationship between the spectacle lens substrate and the print head during the printing process. In other words, the input data is used to determine the geometric relationship between the surface of the spectacle lens substrate and the print head.

[0128] This geometric relationship can be described by at least one parameter selected from the group consisting of a displacement vector, a velocity vector, an incident angle α, a distance Δ, and an arc length s. Thus, at least one parameter describing the geometric relationship can be used to individually determine the printing parameter value of at least one adjustable printing parameter for each print nozzle group. At least one parameter, preferably more than one parameter or even all parameters, can be selected and used to individually determine the printing parameter value.

[0129] Taking into account this geometric relationship, for each nozzle or nozzle group of the print head, it is possible to determine (e.g., calculate) the individual fine-grained and optimized printing parameter values of at least one printing parameter. In other words, determining the printing parameter values with respect to the geometric characteristics allows for improving the printing quality on the curved surface by individually controlling each print nozzle group. There is no need for a complex positioning system or robot to compensate for the general settings of the printing parameters by positioning the spectacle lens substrate and the print head relative to each other.

[0130] For example, the input data can be obtained by receiving input data via wired or wireless transmission from a storage unit for storing the geometric characteristics of different spectacle lens substrates and / or print heads. Other possible ways are to manually or automatically input the geometric characteristics using an input unit coupled to the data processing system that executes the method of the present invention. The geometric characteristics can be provided, for example, in the form of tabular values, or the geometric characteristics can be directly measured and processed using a suitable measuring system. A combination is also possible.

[0131] Optionally, the input data can also include data related to environmental conditions, non-adjustable ink characteristics, and / or material characteristics of the spectacle lens substrate. Accordingly, the printing parameter values of at least one adjustable printing parameter for each print nozzle group can be individually determined depending on the data related to environmental conditions, non-adjustable ink characteristics, and / or material characteristics of the spectacle lens substrate.

[0132] By taking these additional influencing factors into account when determining the printing parameter values, the printing process can be better adapted to the overall conditions and the printing result can be further improved. For example, when deriving at least one of the parameter mappings described below, these additional influencing factors can be considered, i.e., the parameter mapping not only describes the geometric relationship between the spectacle lens substrate and the print head during the printing process, but also includes other influencing factors that may affect the printing process.

[0133] In a specific development, the method step of separately determining the printing parameter values of at least one adjustable printing parameter derives a parameter mapping that includes assigning printing parameter values to a group of data points on the surface of the spectacle lens substrate. Deriving the parameter mapping can include converting the surface of the spectacle lens substrate into a data point grid.

[0134] The method step of separately determining the printing parameter values of at least one adjustable printing parameter can also include providing a look-up table that includes the correlation between the parameters describing the geometric relationship between the surface of the spectacle lens substrate and the print head and the printing parameter values of the adjustable printing parameter. Then, separately determining the printing parameter values can include obtaining a set of printing parameter values from the look-up table of the data points.

[0135] Optionally, the parameter mapping can be derived by optimizing a cost function that is applied to the correlation between the parameters describing the geometric relationship between the surface of the spectacle lens substrate and the print head and the printing parameter values of the adjustable printing parameter.

[0136] In other words, for each parameter or combination thereof that describes the geometric relationship between the surface of the spectacle lens substrate and the print head, a certain set of printing parameter values can be assigned. When creating the look-up table, input data related to environmental conditions and material properties can be considered. The look-up table can include optimized printing parameter values for certain data points and a certain print head (i.e., a certain geometric relationship between the spectacle lens substrate and the print head). The same data point stored in this look-up table can exist on many different surfaces.

[0137] To derive the parameter mapping, known geometric features (e.g., as part of the input data, describing the surface of the spectacle lens substrate, such as the true front curve radius) can be used to convert the surface into a data point grid or mesh. Then, these data points can be looped through and the working settings (i.e., a set of printing parameter values) can be looked up in a previously created general look-up table.

[0138] The derived parameter mapping can form a basic reference system to optimize the entire printing parameter space as a function of the angle of incidence, the distance between the nozzle and the substrate, the velocity vector of the print head, the ejection frequency, and the ejection duration, for example, to optimize the dot shape or weight of the ink droplets.

[0139] For example, the parameter mapping can be derived by optimizing a cost function that applies to the correlation between the parameters describing the geometric relationship between the surface of the spectacle lens substrate and the print head and the print parameter values of the adjustable print parameters, such as the correlation stored in a look-up table.

[0140] The optimization of the cost function can be accomplished by using at least one method, which can be selected from the group consisting of the steepest gradient descent method, genetic algorithms, and machine learning. For example, the so-called Broyden-Fletcher-Goldfarb-Shanno algorithm can be used for optimization.

[0141] In addition, machine learning processes can also be used for optimization. This enables the detection and consideration of other influencing factors whose effects have not yet been considered.

[0142] In a further specific development, the print parameter values of at least one adjustable print parameter of each print nozzle group can be determined individually, such that it is not necessary to adjust the inclination angle of the print head relative to the surface of the spectacle lens substrate before and / or during printing.

[0143] For example, during the entire printing process, the surface to be printed and the surface of the print head including the print nozzles can be oriented substantially parallel to each other.

[0144] This avoids a complex hardware arrangement for rotating (e.g., mechanically tilting) the spectacle lens substrate and / or the print head before and / or during printing, which would otherwise be required to optimize the printing result. Only through fully personalized print parameter values, i.e., personalized ejection profiles of the print nozzle groups, can the effects achieved by complex hardware arrangements (such as tilting devices) in the prior art be mimicked.

[0145] Depending on the size of the print head and the surface to be printed, i.e., in the case where the size of the print head allows coverage of the entire surface to be printed, during the printing of a pattern on the surface of the spectacle lens substrate, the postures (i.e., positions and orientations) of both the spectacle lens substrate and the print head can even remain unchanged relative to each other. In other words, without moving the spectacle lens substrate and the print head relative to each other, an improved pattern can be obtained simply by adjusting the print parameter values of one or more adjustable print parameters. This can allow for a more simplified hardware arrangement.

[0146] According to another aspect of the present invention, there is provided a data processing system including a processor and a storage medium coupled to the processor, wherein the processor is adapted to determine, based on a computer program stored on the storage medium, the print parameter values of an inkjet printing device for printing a pattern on the surface of a spectacle lens substrate, the inkjet printing device including a print head having a plurality of print nozzles.

[0147] The processor is adapted to group a plurality of printing nozzles into at least two printing nozzle groups and to individually determine the printing parameter values of at least one adjustable printing parameter for each printing nozzle group depending on the geometric relationship between the surface of the spectacle lens substrate and the print head, the geometric relationship being determined by using input data related to the geometric features of the surface of the spectacle lens substrate and the print head. Preferably, at least two printing nozzle groups are to be used in a single pass of printing.

[0148] In other words, the data processing system is configured to perform one of the computer-implemented methods for determining the printing parameter values for an inkjet printing device for printing a pattern on the surface of a spectacle lens substrate, wherein the printing parameter values are individually determined depending on the geometric relationship between the surface of the spectacle lens substrate and the print head as described above. Thus, a description of such a computer-implemented method for determining the printing parameter values for an inkjet printing device for printing a pattern on the surface of a spectacle lens substrate and its advantages is given with reference to the above description.

[0149] According to another aspect of the invention, there is provided a computer program comprising instructions which, when executed by a computer, cause the computer to determine the printing parameter values for an inkjet printing device for printing a pattern on the surface of a spectacle lens substrate, the inkjet printing device comprising a print head having a plurality of printing nozzles. The instructions cause the computer to group the plurality of printing nozzles into at least two printing nozzle groups and to individually determine the printing parameter values of at least one adjustable printing parameter for each printing nozzle group depending on the geometric relationship between the surface of the spectacle lens substrate and the print head, the geometric relationship being determined by using input data related to the geometric features of the surface of the spectacle lens substrate and the print head. Preferably, at least two printing nozzle groups are to be used in a single pass of printing.

[0150] In other words, the computer program comprises instructions for performing one of the computer-implemented methods for determining the printing parameter values for an inkjet printing device for printing a pattern on the surface of a spectacle lens substrate, wherein the printing parameter values are individually determined depending on the geometric relationship between the surface of the spectacle lens substrate and the print head as described above. Thus, a description of such a computer-implemented method for determining the printing parameter values for an inkjet printing device for printing a pattern on the surface of a spectacle lens substrate and its advantages is given with reference to the above description.

[0151] According to another aspect of the present invention, there is provided a non-transitory computer-readable storage medium including instructions which, when executed by a computer, cause the computer to determine print parameter values for an inkjet printing apparatus for printing a pattern on a surface of an ophthalmic lens substrate, the inkjet printing apparatus including a print head having a plurality of print nozzles. The instructions cause the computer to group the plurality of print nozzles into at least two print nozzle groups and to individually determine print parameter values for at least one adjustable print parameter of each print nozzle group depending on a geometric relationship between the surface of the ophthalmic lens substrate and the print head, the geometric relationship being determined by using input data related to geometric features of the surface of the ophthalmic lens substrate and the print head. Preferably, at least two print nozzle groups are to be used within a single pass of printing.

[0152] In other words, the non-transitory computer-readable storage medium includes instructions for performing one of computer-implemented methods for determining print parameter values for an inkjet printing apparatus for printing a pattern on a surface of an ophthalmic lens substrate, wherein the print parameter values are individually determined depending on the geometric relationship between the surface of the ophthalmic lens substrate and the print head as described above. Thus, an explanation of such a computer-implemented method for determining print parameter values for an inkjet printing apparatus for printing a pattern on a surface of an ophthalmic lens substrate and its advantages is described with reference to the above.

[0153] According to another aspect of the present invention, there is provided a method for inkjet printing, wherein a pattern is printed on a surface of an ophthalmic lens substrate by an inkjet printing apparatus including a print head having a plurality of print nozzles using print parameter values of at least one adjustable print parameter. The print parameter values of the at least one adjustable print parameter are determined according to a computer-implemented method, wherein the print parameter values are individually determined depending on the geometric relationship between the surface of the ophthalmic lens substrate and the print head as described above.

[0154] In other words, after determining the print parameter values of at least one adjustable print parameter by a computer-implemented method for determining the print parameter values of an inkjet printing device for printing a pattern on the surface of an ophthalmic lens substrate, the inkjet printing device includes a print head having a plurality of print nozzles, wherein the method includes: grouping the plurality of print nozzles into a plurality of print nozzle groups and individually determining the print parameter values of at least one adjustable print parameter for each print nozzle group depending on the geometric relationship between the surface of the ophthalmic lens substrate and the print head, and the determined print parameter values can be used for actual printing. Thus, a description of a computer-implemented method for determining the print parameter values of an inkjet printing device for printing a pattern on the surface of an ophthalmic lens substrate and its advantages is described above, wherein the print parameter values are individually determined depending on the geometric relationship between the surface of the ophthalmic lens substrate and the print head. For example, the inkjet printing method can be used for coloring using a coating or diffusion process, permanent or temporary marking of the lens, masking layer, adhesive layer dots (e.g., increasing surface roughness for coating), additive manufacturing, etc.

[0155] In a specific development of this inkjet printing method, the inclination angle of the print head relative to the surface of the ophthalmic lens substrate is not adjusted before and / or during printing.

[0156] For example, during the entire printing process, the surface to be printed and the surface of the print head including the print nozzles can be oriented substantially parallel to each other.

[0157] This avoids a complex hardware arrangement for rotating (e.g., mechanically tilting) the ophthalmic lens substrate and / or the print head before and / or during printing, which would otherwise be required to optimize the printing result. Only via fully personalized print parameter values, i.e., personalized ejection profiles of the print nozzle groups, can the effects achieved by complex hardware arrangements (such as tilting devices) in the prior art be mimicked.

[0158] Depending on the size of the print head and the surface to be printed, i.e., in the case where the size of the print head allows covering the entire surface to be printed, during printing a pattern on the surface of the ophthalmic lens substrate, the postures (i.e., positions and orientations) of both the ophthalmic lens substrate and the print head can even remain unchanged relative to each other. In other words, without moving the ophthalmic lens substrate and the print head relative to each other, an improved pattern can be obtained simply by adjusting the print parameter values of one or more adjustable print parameters. This can allow for a more simplified hardware arrangement.

[0159] According to another aspect of the present invention, there is provided an inkjet printing apparatus for printing a pattern on the surface of an ophthalmic lens substrate. The inkjet printing apparatus includes a print head having a plurality of printing nozzles and a data processing system including a processor and a storage medium coupled to the processor, wherein the processor is adapted to determine print parameter values based on a computer program stored on the storage medium. The processor is adapted to group the plurality of printing nozzles into at least two print nozzle groups and separately determine the print parameter values of at least one adjustable print parameter for each print nozzle group depending on the geometric relationship between the surface of the ophthalmic lens substrate and the print head, the geometric relationship being determined by using input data related to the geometric features of the surface of the ophthalmic lens substrate and the print head. Preferably, at least two print nozzle groups are to be used in a single pass printing.

[0160] The inkjet printing apparatus is configured to perform the method for inkjet printing as described above. Accordingly, reference is made to the description of the method for inkjet printing (wherein a pattern is printed on the surface of an ophthalmic lens substrate) and its advantages as described above.

[0161] According to another aspect of the present invention, there is provided a data set in the form of a computer-readable data signal, the data set including at least one of the following types of data: (i) a virtual representation of the inkjet printing apparatus as described above, the virtual representation being configured to be fed into one or more manufacturing machines to manufacture the apparatus, or (ii) data containing computer-readable instructions for controlling one or more manufacturing machines to manufacture the inkjet printing apparatus as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0162] Further features, characteristics and advantages of the present invention will become apparent from the following description of embodiments in conjunction with the accompanying drawings.

[0163] Figure 1 Schematically shows an inkjet print head moving on the curved surface of an ophthalmic lens substrate according to the prior art during a printing process.

[0164] Figure 2 Shows a plan view from below of a print head having a plurality of printing nozzles according to the prior art.

[0165] Figure 3 Shows a typical voltage curve applied to the nozzles of an inkjet print head according to the prior art.

[0166] Figure 4 Schematically shows the surface of an ophthalmic lens substrate (half-cut side view).

[0167] Figure 5 Schematically shows the print head passing over the surface of an ophthalmic lens substrate (top view).

[0168] Figure 6 Shows the x, y, z discrete positions of the points forming the front surface of the spectacle lens substrate (parameters D = 50.0 mm, r = 425.0 mm). Three arrows depict Figure 5 the x, y paths of the three single printhead nozzles shown in

[0169] Figure 7 during the printing process Figure 5 the calculated height differences between the three printing nozzles shown and the surface of the spectacle lens substrate.

[0170] Figure 8 Shows the normal vector n(x, y, z) of the front surface of the spectacle lens substrate (parameters D = 50.0 mm, r = 425.0 mm) and Figure 5 the angle of incidence α(x, y, z) between the ink jet (0, 0, -1) of the three printing nozzles shown.

[0171] Figure 9 Shows Figure 5 the angles of incidence of the three printing nozzles shown along their paths.

[0172] Figure 10 Is a flowchart showing an embodiment of a computer-implemented method for determining print parameter values.

[0173] Figure 11 Schematically shows a printhead having a set of printing nozzles.

[0174] Figure 12 Is a flowchart showing another embodiment of a computer-implemented method for determining print parameter values.

[0175] Figure 13 Shows a block diagram of yet another embodiment of a computer-implemented method for determining print parameter values.

[0176] Figure 14 Schematically shows an embodiment of an inkjet printing device.

[0177] Figure 15 Shows a Recon image of the printed surface of a spectacle lens substrate having a diameter of 65 mm and the identified profile.

[0178] Figure 16 Shows another Recon image of the printed surface. The wax pattern overlaps the read nozzle array data.

[0179] Figure 17 Shows the original microscopic image of tile #5 from the surface printed with a norm value of 50.

[0180] Figure 18shows a black-and-white threshold microscopic image derived from the Figure 17 shown image.

[0181] Figure 19 shows a microscopic image of the main features with markers and satellites Figure 17 thereof.

[0182] Figure 20 shows the average circularity of the main features depending on the relative radius and the applied value of the norm.

[0183] Figure 21 shows the number of satellites per tile depending on the relative radius and the applied value of the norm.

[0184] Figure 22 shows a graphical representation of the cost function depending on the relative radius and the applied value of the norm.

[0185] Figure 23 shows a graphical representation of another cost function depending on the relative radius and the applied value of the norm. Detailed Description

[0186] Figure 1 demonstrates the technical problem behind the present invention. A pattern is printed on the curved surface 3 of the spectacle lens substrate 4 using an inkjet printing device including a print head 2 having a plurality of print nozzles 6. The print nozzles 6 eject ink droplets 9 which are deposited on the surface 3 of the spectacle lens substrate 4.

[0187] As Figure 2 shown, a typical print head 2 can include, for example, 880 print nozzles 6 which are arranged in multiple columns and rows at a specific pitch. For example, 300 print nozzles 6 can be arranged per inch in the x direction, thereby producing a print resolution or pixel density of 300 dots per inch (dpi) respectively.

[0188] According to the prior art, all the print nozzles are uniformly controlled, i.e., all the print nozzles 6 use the same print parameter value 1 of the adjustable print parameters 8. As long as the surface 6 of the spectacle lens substrate 4 is uniform, for example flat, this results in a uniform printed image. However, if the surface 6 of the spectacle lens substrate 4 is non-uniform, for example exhibits a curved surface 6 as Figure 1 shown, it will have an adverse effect on the printing result. This is due to the different distances Δ1, Δ2 between the print nozzles 6 and the surface 3 of the spectacle lens substrate 4. Typically, the minimum distance Δ1 between the print nozzles 6 and the surface 3 of the spectacle lens substrate 4 is less than 5 mm. Its relative position-related value Δ2 varies and typically increases towards the outer part of the spectacle lens substrate 4.

[0189] Figure 3Shows a typical voltage curve applied to the printing nozzle 6 during the printing process. It can be divided into several stages, namely the stationary stage, the pre-fill stage, the ejection stage, and the refill / cancellation stage. According to the prior art, the same voltage curve is applied to all printing nozzles. In order to adapt the printing process and affect the overall printing quality, the voltage curve can be changed. For example, the minimum and maximum voltages, slopes, and / or durations of each stage can be changed. The printing parameters 8 adjustable by changing the voltage curve are the ejection frequency, waveform, and norm.

[0190] Figure 4 Schematically depicts a half-sectional side view of the curved surface 3 of the spectacle lens substrate 4: n is the normal vector at any point on the surface 3; j is the ejection vector at which the ejected ink is transferred from the nozzle 6 to the surface 3; α is the angle of incidence between the normal vector n and the ejection vector j; r is the true front curve (true radius of curvature) of the surface 3 when derived from a sphere; dx, dy ( Figure 4 not shown in the figure) and dz are the discrete differences within the coordinate system used; s is the approximate arc length between two points on the surface 3.

[0191] Figure 5 Depicts a top view of the surface 3 of the spectacle lens substrate 4 with diameter D and the movement paths of three different printing nozzles 6a, 6b, 6c of the print head 5 along the x and y directions during the printing process, that is, the case where the print head 5 and the surface 3 move linearly relative to each other along the movement direction m.

[0192] Reference Figures 6 to 9 further explains the effects associated with printing on the exemplary surface 3 shown in Figure 4 and Figure 5 The exemplary ejection vector j is selected as 0, 0, -1. Figure 6 Depicts the discrete x, y, z positions of the points forming the front surface 3 of the spectacle lens substrate 4 (parameters D = 50.0 mm, r = 425.0 mm). Three arrows depict the Figure 5 x, y paths of the three single printing nozzles 6a, 6b, 6c shown in Figure 6 during the printing process. In Figure 6 the z positions are represented by numbers from 424.150 to 424.900. However, it should be noted that the z positions change gradually and cannot be depicted in

[0193] Figure 7 Shows the corresponding calculated height curves between the printing nozzles 6a, 6b, 6c and the surface 3 during the printing process, that is, along Figure 6The z-position of the arrow in []. The minimum distance Δ1 between the printing nozzle 6 and the surface 3 of the spectacle lens substrate 4 is 1 mm.

[0194] As can be seen from Figure 6 and Figure 7 the height difference of the printing nozzle 6a along the path is much larger than that of the printing nozzles 6b, 6c. This results in inconsistent printing results, that is, if optimized for the center of the surface 3, the overall printing quality will seriously decline towards the edge of the spectacle lens substrate 4.

[0195] Figure 8 depicts the x, y discrete positions of the points forming the front surface 3 (parameters D = 50.0 mm, r = 425.0 mm) of the spectacle lens substrate 4. The three arrows depict Figure 5 the x, y paths of the three single printing nozzles 6a, 6b, 6c shown in [] during the printing process. In Figure 8 the incident angle α at different x, y positions is represented by numbers ranging from 0.400 to 3.600. However, it should be noted that the incident angle α changes gradually and cannot be depicted in Figure 8 due to the required drawing format. Therefore, the noted values of the incident angle α are only exemplary to represent the general route of the incident angle α. Figure 9 shows the incident angle α depending on the x-position of the printing nozzles 6a, 6b, 6c, that is, the incident angle α of the arrow in Figure 8 The incident angle α varies between 0° and greater than 3.5°, where the printing nozzle 6a deviates much more than the printing nozzles 6b, 6c. Generally, the incident angle α increases towards the edge of the spectacle lens substrate 4. Regarding Figure 6 and Figure 7 as explained, this amplifies the inconsistent printing results already caused by the height difference, that is, if optimized for the center of the surface 3, the overall printing quality will decline more towards the edge of the spectacle lens substrate 4.

[0196] As the distance Δ between the printing nozzle 6 and the surface 3 of the spectacle lens substrate 4 increases and the incident angle α increases, the inventors of the present invention can observe an obvious dispersion trend in the printing results, that is, multiple small dots appear.

[0197] In order to reduce the influence that adversely affects the printing quality as described above, a computer-implemented method 100 for determining the printing parameter value 1 of an inkjet printing device 2 for printing a pattern on the surface 3 of a spectacle lens substrate 4 is proposed. The inkjet printing device 2 includes a print head 5 having a plurality of printing nozzles 6. Figure 10 The flowchart shown refers to the first embodiment of such a method 100.

[0198] In a first step S1, input data 8 is obtained that relates to the geometry of the surface 3 of the ophthalmic lens substrate 4 and the printhead 5 of the inkjet printing device 2. This data can include data on the topological shape of the surface 3 of the ophthalmic lens substrate 4 (e.g., its diameter D, its true front curve r) and geometric data on the printhead 5 (e.g., its orientation, the number of print nozzles 6, the spacing of the print nozzles 6, etc.). For example, the diameter D can be 50 mm and the true curve r can be 425.0 mm. The printhead 5 can include 880 print nozzles 6 with a nozzle pitch of 300 per inch in the x direction.

[0199] In step S2, the plurality of print nozzles 6 are grouped into five print nozzle groups 10a, 10b, 10c, 10d, 10e. The exact amount of print nozzle groups 10a, 10b, 10c, 10d, 10e can vary depending on the geometric characteristics of the ophthalmic lens substrate 4 and / or the desired printing quality. At least two of the five print nozzle groups 10a, 10b, 10c, 10d, 10 are to be used within a single pass of printing. Optionally, all five print nozzle groups 10a, 10b, 10c, 10d, 10 are to be used within a single pass of printing.

[0200] Figure 11 The printhead 5 and its print nozzles 6 are shown, which are grouped into five print nozzle groups 10a, 10b, 10c, 10d, 10e that are symmetrically arranged with respect to the direction of movement m of the printhead 5. Towards the edge, two print nozzle groups 10a, 10e are arranged, which include the fewest print nozzles 6. As for the center, two print nozzle groups 10b, 10d are arranged, which include more print nozzles 6. The print nozzle group 10c in the center includes the most print nozzles 6. As Figure 7 and Figure 9 shown, this amount of print nozzle groups 10a, 10b, 10c, 10d, 10e and their arrangement are caused by the height difference and the route of the angle of incidence α being steeper towards the edge and flatter in the center.

[0201] Referring again to Figure 10 , in step S3, the print parameter values 1 of the adjustable print parameters 7 for each print nozzle group 10a, 10b, 10c, 10d, 10e are determined individually. For example, the print parameter values 1 of one or more of the print parameters 7 for each print nozzle group 10a, 10b, 10c, 10d, 10e can be determined individually, the print parameters being selected from the group consisting of ejection temperature, ejection duration, ejection frequency, fan value, waveform parameters, and adjustable ink characteristics.

[0202] Afterwards, the printing parameter values 1 determined for each printing nozzle group 10a, 10b, 10c, 10d, 10e can be used to print a pattern on the surface 3 of the spectacle lens substrate 4. Optionally, the inclination angle of the print head 5 relative to the surface 3 of the spectacle lens substrate 4 is not adjusted before and / or during printing.

[0203] Figure 12 A flowchart depicting another embodiment of a computer-implemented method 100 for determining printing parameter values 1 of an inkjet printing device 2 for printing a pattern on the surface 3 of a spectacle lens substrate 4. Regarding steps S1 and S2, reference Figure 10 description.

[0204] Step S3, which is the step of individually determining the printing parameter values 1 of the adjustable printing parameters 7, 7a, 7b, 7c, 7d, 7e, 7f for each printing nozzle group 10a, 10b, 10c, 10d, 10e, includes sub-steps S4 to S6.

[0205] In step S4, a look-up table 13 and a cost function are provided. For example, the look-up table 13 can be retrieved from a storage medium. The look-up table 13 contains the correlation between the parameters 11, 11a, 11b, 11c that describe the geometric relationship between the surface 3 of the spectacle lens substrate 4 and the print head 5 and the adjustable printing parameters 7, 7a, 7b, 7c, 7d, 7e, 7f. The cost function can be a general cost function or a cost function dedicated to a special purpose, i.e., considering quality parameters related to the special purpose situation.

[0206] In step S5, the cost function is applied to the look-up table 13 and optimized to retrieve the appropriate printing parameter values 1 corresponding to the input data 8, 8a, 8b, 8c, 8d. In other words, the printing parameter values 1 that result in the minimum total cost are retrieved from the look-up table 13. For example, considering the entire surface 3 of the spectacle lens substrate 4 to be printed, the amount of satellites as a quality parameter may be the least. The optimization of the cost function can be accomplished by using at least one method that can be selected from the group consisting of the steepest gradient descent method, genetic algorithms, and machine learning.

[0207] In step S6, a parameter map 12 is derived taking into account the optimization result. The parameter map includes the assignment of the printing parameter values 1 to specific point groups on the surface 3 of the spectacle lens substrate 4. In other words, the printing parameter values 1 are individually determined for each printing nozzle group 10a, 10b, 10c, 10d, 10e and stored as the parameter map 12.

[0208] Thereafter, the pattern can be printed on the surface 3 of the ophthalmic lens substrate 4 using the printing parameter values 1 determined for each printing nozzle group 10a, 10b, 10c, 10d, 10e (i.e., the parameter map 12). If it is impossible to correct the printing parameter values 1 during a printing process, for example, the gray level cannot be changed, the actual printing parameter values 1 and their distribution can be discretized into, for example, four parts from 0 to radius R, where several sub-images (e.g., four sub-images) are printed with different printing parameter values (e.g., four “rings” cooperating with each other) instead of one image.

[0209] Figure 13 The block diagram shown illustrates yet another embodiment of a computer-implemented method 100 for determining printing parameter values 1 of an inkjet printing device 2 for printing a pattern on the surface 3 of an ophthalmic lens substrate 4.

[0210] This method 100 is based on the finding that each surface point of the surface 3 of the ophthalmic lens substrate 4 to be printed should be considered individually by calculating and applying optimized printing parameters 7a, 7b, 7c, 7d, 7e, 7f. The required input data 8a, 8b, 8c, 8d obtained in step S1 relate to the geometric characteristics of the surface 3 of the ophthalmic lens substrate 4 (i.e., the geometric shape of the lens), the print head 5 which is part of the inkjet printing device 2, and optionally the ink 9 and / or the environmental conditions and material properties of the ophthalmic lens substrate 4.

[0211] From this input data 8a, 8b, 8c, 8d, the parameter values of parameters 11a, 11b, 11c which describe the geometric relationship between the surface 3 of the ophthalmic lens substrate 4 and the print head 5 can be derived. These parameter values describe the “inkjet printing device - ophthalmic lens substrate” system during the printing process. Preferred parameters 11a, 11b, 11c include, for example, the angle of incidence α, displacement vector, velocity vector, distance Δ, and arc length s.

[0212] In step S3, the printing parameter values 1 of the printing parameters 7a, 7b, 7c, 7d, 7e, 7f are calculated for each printing nozzle group 10a, 10b, 10c, 10d, 10e created previously in step S2. The printing parameters 7a, 7b, 7c, 7d, 7e, 7f considered in this embodiment are the ejection temperature, ejection duration, ejection frequency, norm value, waveform parameter, and adjustable ink properties. Other settings and / or characteristics can also be considered.

[0213] To retrieve the printing parameter value 1, a look-up table 13 is provided in step S4. The look-up table is pre-created and includes the correlation of the parameters 11a, 11b, 11c that describe the geometric relationship between the surface 3 of the spectacle lens substrate 4 and the print head with the printing parameter value 1 of the adjustable printing parameters 7a, 7b, 7c, 7d, 7e, 7f. The printing parameters 7a, 7b, 7c, 7d, 7e, 7f can be understood as functions. For each parameter 11a, 11b, 11c or combination thereof that describes the geometric relationship between the surface 3 of the spectacle lens substrate 4 and the print head 5, a certain set of printing parameters 7a, 7b, 7c, 7d, 7e, 7f is assigned. When creating the look-up table 13, the input data 8c, 8d related to environmental conditions and material properties can be considered.

[0214] Moreover, a cost function is provided, which is applied to the look-up table 13 and optimized in step S5. Finally, in step S6, the parameter mapping 12 is retrieved from the optimized cost function. The printing parameters 7a, 7b, 7c, 7d, 7e, 7f assigned to a specific set of points on the surface 3 of the spectacle lens substrate 4 are stored as the parameter mapping 12.

[0215] Figure 14 An embodiment of an inkjet printing device 2 using drop-on-demand inkjet technology is depicted. The inkjet printing device 2 includes a print head 5 having a plurality of printing nozzles 6. Moreover, the inkjet printing device 2 includes a data processing system 200, which includes a processor 20 and a storage medium 21 coupled to the processor 20 (represented by the double arrows in Figure 14 . The processor 20 is adapted to group the plurality of printing nozzles 6 into at least two printing nozzle groups 10a, 10b, 10c, 10d, 10e and to individually determine the printing parameter value 1 of at least one adjustable printing parameter 7, 7a, 7b, 7c, 7d, 7e, 7f for each printing nozzle group 10a, 10b, 10c, 10d, 10e based on a computer program stored on the storage medium 21. The storage medium 21 can also be used for storing the look-up table 13 and / or the retrieved parameter mapping 12. In other words, the data processing system 200 can execute one of the computer-implemented methods described herein for determining the printing parameter value 1. The determined printing parameter value 1 can be transmitted to the print head 5 and its printing nozzles 6 to perform the printing process.

[0216] Reference Figures 15 to 23 , the creation of the look-up table 13 and the retrieval of the parameter mapping 12 are described in more detail below.

[0217] In this embodiment, a hot melt printing technique is used to print wax micro - droplets in a unique pattern on the convex surface 3 of the spectacle lens substrate 4. The surface 3 and the applied wax pattern are photographed using an industrial microscope. The images obtained for specific patches of the printed wax pattern are analyzed in terms of the roundness of the applied micro - droplets and the number of satellites formed (small micro - droplets, scattered micro - droplets, and adverse micro - droplets). These characteristics can be quantified and used as examples of printing quality parameters.

[0218] Using a Zeiss Recon system, overview images of the entire surface 3 of the spectacle lens substrate 4 are obtained, and the relative patch positions of the applied wax pattern are reconstructed from these images. Combining the data collected from the microscope and the Recon system, the calculated quality parameter values are related to the position of the underlying patches on the surface 3. This information is used to derive a look - up table 13 for suitable values of the printing parameters 7, 7a, 7b, 7c, 7d, 7e, 7f for printing on the surface 3 of the spectacle lens substrate 4.

[0219] The experimental procedure includes: hot melt printing (splash - ink, without movement) on the surface 3 of the spectacle lens substrate 4 using different settings of the nominal values of the ink - jet printing device 2; taking Recon images of the printed surface 3; analyzing the Recon images for patch localization; taking microscopic images of different patches of the applied pattern; defining quality parameters and analyzing the microscopic images; mapping the quality parameters on the surface 3; and running an optimizer to prepare a lens - specific parameter map 12.

[0220] Printing on the surface of the spectacle lens substrate

[0221] The printing is done using a Teco printing press with a Xerox M1 print head. From the technical data sheet of the Xerox M1 print head series, the absolute and relative positions of the individual printing nozzles 6, 6a, 6b, 6c are known. Based on this information, an (x, y) array of the individual nozzles can be derived and used to identify individual patches during image analysis. During a standard printing process, it is known which printing nozzles 6, 6a, 6b, 6c pass over which parts of the surface 3, and the nozzle firing sequence is calculated accordingly.

[0222] First, the positioning system is used to position the ophthalmic lens substrate 4 to be printed under the print head 5. Then, the "splash ink" function of the print head 5 is used to apply wax onto the surface 3 of the ophthalmic lens substrate 4. During "splash ink", the ophthalmic lens substrate 4 does not move. The pattern formed on the surface 3 corresponds to the grid defined by the nozzle plate of the Xerox M1 print head. In the experiment, five emissions (waveform repetition - 10 Hz, 500 ms) were respectively performed on six ophthalmic lens substrates 4 with the same geometry and the minimum distance to the print head 5. Among these ophthalmic lens substrates 4, the nominal values of the printing parameters 7, 7a, 7b, 7c, 7d, 7e, 7f were increased from 20 to 60 in steps of 10.

[0223] Acquisition and analysis of the Recon image

[0224] The relative and absolute positions of the grid tiles on the surface 3 of the ophthalmic lens substrate 4 can be reconstructed from the Recon image. The Zeiss Recon system is a system for obtaining high-quality images of ophthalmic lenses to detect, for example, laser engravings and similar structures. In this example, the Recon system is used to detect the (x, y) positions of individual wax droplets. Regarding the software, OpenCV and Python are used to analyze the Recon image.

[0225] In Figure 15 , the outer contour of the ophthalmic lens substrate 4 and its center (pixel coordinates in the image) are shown. The center has been determined by minimizing the sum of the squared distances from the center to the points forming the lens contour. Knowing the position of the lens center, the average distance from it to all the contour points of the ophthalmic lens substrate 4 is calculated. From these numbers and the known physical diameter (65 mm) of the ophthalmic lens substrate 4, the appropriate scale factor (pixels to microns) can be calculated.

[0226] In a further step, OpenCV identifies the applied wax droplets, and their positions partially overlap with the markers ( Figure 15 the black dots in ). Around these markers, convex hulls are constructed, and unit vectors are derived using three of the points (marked as large black dots) among them. These vectors are needed to construct a rotation matrix to align the image and the coordinate system of the read-in nozzle positions of the print head 5. The center position of the surface 3 from the Recon image is also used for the (x, y) translation of the read-in nozzle array.

[0227] In Figure 16 , the printed wax dots overlap with the "theoretical" positions of the printing nozzles 6, 6a, 6b, 6c (black dots), and they are well aligned with the observed wax dots. The points (coordinates of the "real" droplets) in the tiles for microscopic analysis are depicted as crosses.

[0228] Acquisition and analysis of the microscopic image

[0229] The microscopic images were obtained using a Zeiss Smart Zoom 5 microscope. The microscope was tilted according to the tile position on the surface 3 of the spectacle lens substrate 4 to minimize the defocused area and maximize the contrast. The settings for microscopic image acquisition were as follows: microscope type - image, objective - 5, magnification - 101x, resolution - 2.2040μm px -1 , exposure time 0.2819 ms, illumination - upper right light.

[0230] For the Recon images, OpenCV and Python were used to analyze the microscopic images. Figure 17 Tile 5 in the surface 3 printed with a value of 50 is depicted. In Figure 16 the "Recon" image, the center point of this tile was marked. From the center point to the top of the image, on the left side, it is the fifth of eight black crosses.

[0231] The first step of image analysis was to convert the original image to grayscale. Secondly, Gaussian blur was applied to the image to remove pixel noise that affects contour recognition ( Figure 18 ). The necessary "pre - processing" of the image depends on the analysis technique employed and the experimental settings used. For example, Gaussian blur with a kernel size of 15 was best for identifying large dots ("main features"). For the detection of smaller - sized satellites, Gaussian blur with a kernel size of 5 was used.

[0232] From the Gaussian - blurred grayscale image, a black - and - white image can be obtained using an adaptive thresholding function. The parameters used here were (111 - 6) for the detection of main features and (141 - 6) for satellite detection. In Figure 19 the thresholded black - and - white image for the detection of main features is shown. Contour recognition was performed on the black - and - white image, and the detected spots were classified as main features (A < 300 px 2 ) or satellites (20 px 2 < A < 300 px 2 ). The first quality parameter obtained was the number of satellites per tile (the more, the worse). The second quality parameter was the roundness of the detected main features (equal to one for a perfect circle, see Equation (I)).

[0233] C = 4 * π * A / P 2 Equation (I)

[0234] where, C = roundness, A = the area of the spot in square pixels, P = the perimeter of the spot in pixels

[0235] Figure 19 The detected main features were marked with a dashed - line rectangle and the detected satellites were marked with black dots in

[0236] Parameter mapping and optimization

[0237] For each analyzed microscopic image, the quality parameters obtained (roundness of the average feature and number of satellites) are attributed to the center point of the corresponding tile obtained from the Recon image. For convenience, the calculated (x,y) points are represented as the relative radius of the spectacle lens substrate 4 with a diameter of 65 mm (see Figures 20 to 22 for the y-axis in). To systematically build a database or lookup table 13, the surface-to-nozzle distance is preferably used as a non-lens-specific characteristic.

[0238] Figure 20 and Figure 21 Each black cross in represents an experimentally tested setting. Linear interpolation is performed between these support points using a finer mesh. Visually, a norm value of 40 seems to be a good choice for the applied conditions. Regarding the number of satellites formed, a norm value of 40 also seems good. Finally, the aim is to define a cost function based on appropriate quality parameters to optimize the printing process.

[0239] As an example, the function shown in equation (II) is used to create Figure 22 , i.e., to calculate the cost depending on different relative radii and norm values, where the number of satellites formed and roundness are considered as quality parameters.

[0240] Cost = gridz1 / (gridz0)3 Equation (II)

[0241] The variable gridz1 represents the number of satellites per tile, and the variable gridz0 represents the average roundness of the detected droplets. Given that this cost function must range from 0 to 1 (relative radius of the spectacle lens substrate 4), an optimizer can be used to find the "cheapest" route and include additional constraints if necessary. For example, depending on the specific application, the cost function can focus on satellites or roundness. The "cheapest route" in this particular example is marked with a black arrow, and the corresponding norm value is 20. By defining different cost functions, different cheapest routes will be obtained, which are not necessarily straight lines.

[0242] Figure 22 The black arrow in actually represents a graphical representation of the parameter mapping 12, which includes the determined printing parameter value 1, i.e., the norm value 20. In other cases, the determined optimized norm value may vary with the relative radius, such that different norm values are determined for different printing nozzle groups 10a, 10b, 10c, 10d, 10e.

[0243] Figure 23 shows the one related to Figure 22Similar graphical representations, in which different cost functions (Equation (III)) are used

[0244] Cost = Cost = gridz1 / (gridz0)2 Equation (III)

[0245] Since in Equation (III) the number of satellites is less obvious compared to Equation (II), i.e., (gridz1)2 instead of (grindz1)3, the influence of the two quality parameters is more balanced.

[0246] Preferred features of the present invention are:

[0247] 1. A computer-implemented method for determining the values of printing parameters of an inkjet printing device for printing a pattern on the surface of an ophthalmic lens substrate, the inkjet printing device comprising a print head having a plurality of printing nozzles, wherein the method comprises:

[0248] - Grouping the plurality of printing nozzles into at least two printing nozzle groups, and

[0249] - Individually determining the values of at least one adjustable printing parameter for each printing nozzle group.

[0250] 2. The method according to clause 1, wherein the at least one adjustable printing parameter is selected from the group consisting of ejection temperature, ejection duration, ejection frequency, fan value, waveform parameter, and adjustable ink characteristics.

[0251] 3. The method according to clause 1 or clause 2, wherein each printing nozzle group comprises a single printing nozzle.

[0252] 4. The method according to any one of clauses 1 to 3, wherein the method comprises:

[0253] - Obtaining input data related to the surface of the ophthalmic lens substrate and the geometric characteristics of the print head,

[0254] wherein the printing parameter values are individually determined depending on the input data.

[0255] 5. The method according to clause 4, wherein the input data is used to determine the geometric relationship between the surface of the ophthalmic lens substrate and the print head, wherein the geometric relationship is described by at least one parameter selected from the group consisting of displacement vector, velocity vector, incident angle α, distance Δ, or arc length s.

[0256] 6. The method according to clause 4 or clause 5, wherein the input data includes data related to environmental conditions, non-adjustable ink characteristics, and / or material characteristics of the ophthalmic lens substrate.

[0257] 7. The method according to any one of clauses 1 to 6, wherein the method step of separately determining the printing parameter values of at least one adjustable printing parameter includes deriving a parameter map, which includes assigning printing parameter values to a specific set of points on the surface of the spectacle lens substrate.

[0258] 8. The method according to clause 7 in combination with at least clause 5, wherein the parameter map is derived by optimizing a cost function, which is applied to the correlation between the parameters describing the geometric relationship between the surface of the spectacle lens substrate and the print head and the adjustable printing parameters.

[0259] 9. The method according to clause 8, wherein the optimization uses at least one method selected from the group consisting of the steepest gradient descent method, genetic algorithms, and machine learning.

[0260] 10. The method according to clause 8 or clause 9, wherein the cost function defines the cost depending on quality parameters.

[0261] 11. The method according to clause 10, wherein the quality parameters include the number of satellites formed and / or the roundness of the average features printed.

[0262] 12. The method according to any one of clauses 7 to 11, wherein the parameter map is derived by using a look-up table.

[0263] 13. The method according to any one of clauses 1 to 12, wherein the surface of the spectacle lens substrate is a curved surface.

[0264] 14. The method according to any one of clauses 1 to 13, wherein the at least two print nozzle groups are to be used in a single pass of printing.

[0265] 15. The method according to any one of clauses 1 to 14, wherein the printing parameter values of at least one adjustable printing parameter for each print nozzle group are separately determined such that it is not necessary to adjust the inclination angle of the print head relative to the surface of the spectacle lens substrate before and / or during printing.

[0266] 16. The method according to any one of clauses 1 to 15, wherein the printing parameter values of at least one adjustable printing parameter for each print nozzle group are separately determined such that during the printing of a pattern on the surface of the spectacle lens substrate, the postures of both the spectacle lens substrate and the print head remain unchanged relative to each other.

[0267] 17. A data processing system, the data processing system comprising a processor and a storage medium coupled to the processor, wherein the processor is adapted to determine, based on a computer program stored on the storage medium, a printing parameter value for an inkjet printing device for printing a pattern on a curved surface of a spectacle lens substrate, the inkjet printing device comprising a print head having a plurality of printing nozzles, wherein the processor is adapted to group the plurality of printing nozzles into at least two printing nozzle groups and individually determine a printing parameter value for at least one adjustable printing parameter of each printing nozzle group.

[0268] 18. The data processing system according to clause 17, wherein at least one adjustable printing parameter is selected from the group consisting of ejection temperature, ejection duration, ejection frequency, fan value, waveform parameter, and adjustable ink property.

[0269] 19. The data processing system according to clause 17 or clause 18, wherein each printing nozzle group comprises a single printing nozzle.

[0270] 20. The data processing system according to any one of clauses 17 to 19, wherein the processor is adapted to obtain input data related to the surface of the spectacle lens substrate and the geometric features of the print head, and wherein the processor is adapted to individually determine the printing parameter values depending on the input data.

[0271] 21. The data processing system according to clause 20, wherein the processor is adapted to use the input data to determine a geometric relationship between the surface of the spectacle lens substrate and the print head, wherein the geometric relationship is described by at least one parameter selected from the group consisting of a displacement vector, a velocity vector, an incident angle α, a distance Δ, or an arc length s.

[0272] 22. The data processing system according to clause 20 or clause 21, wherein the input data comprises data related to environmental conditions, non-adjustable ink properties, and / or material properties of the spectacle lens substrate.

[0273] 23. The data processing system according to any one of clauses 17 to 22, wherein the processor is adapted to derive a parameter map that includes an assignment of printing parameter values to a specific set of points on the surface of the spectacle lens substrate.

[0274] 24. The data processing system according to clause 23 in combination with at least clause 21, wherein the processor is adapted to derive the parameter map by optimizing a cost function that applies to the correlation between the parameters describing the geometric relationship between the surface of the spectacle lens substrate and the print head and the adjustable printing parameters.

[0275] 25. The data processing system as described in clause 24, wherein the optimization uses at least one method selected from the group consisting of the steepest gradient descent method, genetic algorithms, and machine learning.

[0276] 26. The data processing system as described in clause 24 or 25, wherein the cost function depends on quality parameters to define the cost.

[0277] 27. The data processing system as described in clause 26, wherein the quality parameters include the number of satellites formed and / or the roundness of the average features printed.

[0278] 28. The data processing system as described in any one of clauses 23 to 27, wherein the parameter mapping is derived by using a look-up table.

[0279] 29. The data processing system as described in any one of clauses 17 to 28, wherein the surface of the spectacle lens substrate is a curved surface.

[0280] 30. The data processing system as described in any one of clauses 17 to 29, wherein at least two printing nozzle groups are to be used within a single pass of printing.

[0281] 31. The data processing system as described in any one of clauses 17 to 30, wherein the printing parameter values of at least one adjustable printing parameter for each printing nozzle group are determined individually such that it is not necessary to adjust the inclination angle of the print head relative to the surface of the spectacle lens substrate before and / or during printing.

[0282] 32. The data processing system as described in any one of clauses 17 to 31, wherein the printing parameter values of at least one adjustable printing parameter for each printing nozzle group are determined individually such that the postures of both the spectacle lens substrate and the print head remain unchanged relative to each other during the printing of a pattern on the surface of the spectacle lens substrate.

[0283] 33. A computer program comprising instructions which, when executed by a computer, cause the computer to determine the printing parameter values for an inkjet printing device for printing a pattern on a curved surface of a spectacle lens substrate, the inkjet printing device comprising a print head having a plurality of printing nozzles, wherein the instructions cause the computer to group the plurality of printing nozzles into at least two printing nozzle groups and to determine individually the printing parameter values of at least one adjustable printing parameter for each printing nozzle group.

[0284] 34. The computer program as described in clause 33, wherein the at least one adjustable printing parameter is selected from the group consisting of ejection temperature, ejection duration, ejection frequency, fan value, waveform parameter, and adjustable ink properties.

[0285] 35. A computer program as described in clause 33 or clause 34, wherein each printing nozzle group includes a single printing nozzle.

[0286] 36. A computer program as described in any one of clauses 33 to 35, wherein the instructions cause the computer to obtain input data related to the surface of the spectacle lens substrate and the geometric features of the printhead, and wherein the computer is caused to individually determine the print parameter values depending on the input data.

[0287] 37. A computer program as described in clause 36, wherein the instructions cause the computer to use the input data to determine the geometric relationship between the surface of the spectacle lens substrate and the printhead, wherein the geometric relationship is described by at least one parameter selected from the group consisting of a displacement vector, a velocity vector, an incident angle α, a distance Δ, or an arc length s.

[0288] 38. A computer program as described in clause 36 or clause 37, wherein the input data includes data related to environmental conditions, non-adjustable ink properties, and / or material properties of the spectacle lens substrate.

[0289] 39. A computer program as described in any one of clauses 33 to 38, wherein the instructions cause the computer to derive a parameter map that includes an assignment of print parameter values to a specific set of points on the surface of the spectacle lens substrate.

[0290] 40. A computer program as described in clause 39 in combination with at least clause 37, wherein the instructions cause the computer to derive the parameter map by optimizing a cost function that applies to the correlation between the parameters describing the geometric relationship between the surface of the spectacle lens substrate and the printhead and the adjustable print parameters.

[0291] 41. A computer program as described in clause 40, wherein the optimization uses at least one method selected from the group consisting of the steepest gradient descent method, genetic algorithms, and machine learning.

[0292] 42. A computer program as described in clause 40 or clause 41, wherein the cost function defines the cost depending on quality parameters.

[0293] 43. A computer program as described in clause 42, wherein the quality parameters include the number of satellites formed and / or the roundness of the average features printed.

[0294] 44. A computer program as described in any one of clauses 39 to 43, wherein the parameter map is derived by using a look-up table.

[0295] 45. A computer program as described in any one of clauses 33 to 44, wherein the surface of the spectacle lens substrate is a curved surface.

[0296] 46. A computer program as described in any one of clauses 33 to 45, wherein the at least two printing nozzle groups are to be used within a single pass of printing.

[0297] 47. A computer program as described in any one of clauses 33 to 46, wherein the printing parameter values of at least one adjustable printing parameter for each printing nozzle group are determined separately such that it is not necessary to adjust the inclination angle of the print head relative to the surface of the spectacle lens substrate before and / or during printing.

[0298] 48. A computer program as described in any one of clauses 33 to 47, wherein the printing parameter values of at least one adjustable printing parameter for each printing nozzle group are determined separately such that during the printing of a pattern on the surface of the spectacle lens substrate, the postures of both the spectacle lens substrate and the print head remain unchanged relative to each other.

[0299] 49. A non - transitory computer - readable storage medium, the non - transitory computer - readable storage medium comprising instructions which, when executed by a computer, cause the computer to determine the printing parameter values for an ink - jet printing device for printing a pattern on the curved surface of a spectacle lens substrate, the ink - jet printing device comprising a print head having a plurality of printing nozzles, wherein the instructions cause the computer to group the plurality of printing nozzles into at least two printing nozzle groups and to determine separately the printing parameter values of at least one adjustable printing parameter for each printing nozzle group.

[0300] 50. The non - transitory computer - readable storage medium as described in clause 49, wherein the at least one adjustable printing parameter is selected from the group consisting of ejection temperature, ejection duration, ejection frequency, fan value, waveform parameter, and adjustable ink properties.

[0301] 51. The non - transitory computer - readable storage medium as described in clause 49 or clause 50, wherein each printing nozzle group comprises a single printing nozzle.

[0302] 52. The non - transitory computer - readable storage medium as described in any one of clauses 49 to 51, wherein the instructions cause the computer to obtain input data related to the surface of the spectacle lens substrate and the geometric features of the print head, and wherein the computer is caused to determine the printing parameter values separately depending on the input data.

[0303] 53. The non - transitory computer - readable storage medium as described in clause 52, wherein the instructions cause the computer to use the input data to determine the geometric relationship between the surface of the spectacle lens substrate and the print head, wherein the geometric relationship is described by at least one parameter selected from the group consisting of displacement vector, velocity vector, incident angle α, distance Δ, or arc length s.

[0304] 54. A non-transitory computer-readable storage medium as described in clause 52 or clause 53, wherein the input data includes data related to environmental conditions, non-adjustable ink characteristics, and / or material characteristics of the spectacle lens substrate.

[0305] 55. A non-transitory computer-readable storage medium as described in any one of clauses 49 to 54, wherein the instructions cause the computer to derive a parameter map that includes assigning print parameter values to a specific set of points on the surface of the spectacle lens substrate.

[0306] 56. A non-transitory computer-readable storage medium as described in clause 55 in combination with at least clause 53, wherein the instructions cause the computer to derive the parameter map by optimizing a cost function that applies to the correlation between parameters describing the geometric relationship between the surface of the spectacle lens substrate and the print head and adjustable print parameters.

[0307] 57. A non-transitory computer-readable storage medium as described in clause 56, wherein the optimization uses at least one method selected from the group consisting of the steepest gradient descent method, genetic algorithms, and machine learning.

[0308] 58. A non-transitory computer-readable storage medium as described in clause 56 or clause 57, wherein the cost function defines the cost depending on quality parameters.

[0309] 59. A non-transitory computer-readable storage medium as described in clause 58, wherein the quality parameters include the number of satellites formed and / or the roundness of the average features printed.

[0310] 60. A non-transitory computer-readable storage medium as described in any one of clauses 55 to 59, wherein the parameter map is derived by using a look-up table.

[0311] 61. A non-transitory computer-readable storage medium as described in any one of clauses 49 to 60, wherein the surface of the spectacle lens substrate is a curved surface.

[0312] 62. A non-transitory computer-readable storage medium as described in any one of clauses 49 to 61, wherein the at least two print nozzle groups are to be used in a single pass of printing.

[0313] 63. A non-transitory computer-readable storage medium as described in any one of clauses 49 to 62, wherein the print parameter values of at least one adjustable print parameter for each print nozzle group are determined separately such that it is not necessary to adjust the inclination angle of the print head relative to the surface of the spectacle lens substrate before and / or during printing.

[0314] 64. A non - transitory computer - readable storage medium as described in any one of clauses 49 to 63, wherein the printing parameter values of at least one adjustable printing parameter for each printing nozzle group are determined individually such that during printing a pattern on the surface of an ophthalmic lens substrate, the postures of both the ophthalmic lens substrate and the print head remain unchanged relative to each other.

[0315] 65. A method for ink - jet printing, wherein printing parameter values of at least one adjustable printing parameter are used, and a pattern is printed on the curved surface of an ophthalmic lens substrate using an ink - jet printing device including a print head having a plurality of printing nozzles, and wherein the printing parameter values of at least one adjustable printing parameter are determined according to a computer - implemented method as described in any one of clauses 1 to 16.

[0316] 66. The method as described in clause 65, wherein the pattern is printed for at least one process selected from the group consisting of permanent lens marking, temporary lens marking, application of a masking layer, application of adhesive layer dots, additive manufacturing, and coloring.

[0317] 67. The method as described in clause 65 or clause 66, wherein the inclination angle of the print head relative to the surface of the ophthalmic lens substrate is not adjusted before and / or during printing.

[0318] 68. The method as described in any one of clauses 65 to 67, wherein during printing a pattern on the surface of an ophthalmic lens substrate, the postures of both the ophthalmic lens substrate and the print head remain unchanged relative to each other.

[0319] 69. An ink - jet printing device for printing a pattern on the curved surface of an ophthalmic lens substrate, the ink - jet printing device comprising:

[0320] - A print head having a plurality of printing nozzles, and

[0321] - A data processing system including a processor and a storage medium coupled to the processor, wherein the processor is adapted to determine printing parameter values based on a computer program stored on the storage medium,

[0322] wherein the processor is adapted to group the plurality of printing nozzles into at least two printing nozzle groups and determine individually the printing parameter values of at least one adjustable printing parameter for each printing nozzle group.

[0323] 70. The ink - jet printing device as described in clause 69, wherein at least one adjustable printing parameter is selected from the group consisting of ejection temperature, ejection duration, ejection frequency, fan value, waveform parameter, and adjustable ink properties.

[0324] 71. The ink - jet printing device as described in clause 69 or clause 70, wherein each printing nozzle group includes a single printing nozzle.

[0325] 72. An inkjet printing device as described in any one of clauses 69 to 71, wherein the processor is adapted to obtain input data related to the surface of the spectacle lens substrate and the geometric characteristics of the print head, and wherein the processor is adapted to individually determine the print parameter values depending on the input data.

[0326] 73. An inkjet printing device as described in clause 72, wherein the processor is adapted to use the input data to determine the geometric relationship between the surface of the spectacle lens substrate and the print head, and wherein the geometric relationship is described by at least one parameter selected from the group consisting of a displacement vector, a velocity vector, an incident angle α, a distance Δ, or an arc length s.

[0327] 74. An inkjet printing device as described in clause 72 or clause 73, wherein the input data includes data related to environmental conditions, non-adjustable ink characteristics, and / or material characteristics of the spectacle lens substrate.

[0328] 75. An inkjet printing device as described in any one of clauses 69 to 74, wherein the processor is adapted to derive a parameter map that includes the assignment of print parameter values to a specific set of points on the surface of the spectacle lens substrate.

[0329] 76. An inkjet printing device as described in clause 75 in combination with at least clause 59, wherein the processor is adapted to derive the parameter map by optimizing a cost function that applies to the correlation between the parameters describing the geometric relationship between the surface of the spectacle lens substrate and the print head and the adjustable print parameters.

[0330] 77. An inkjet printing device as described in clause 76, wherein the optimization uses at least one method selected from the group consisting of the steepest gradient descent method, genetic algorithms, and machine learning.

[0331] 78. An inkjet printing device as described in clause 76 or clause 77, wherein the cost function defines the cost depending on quality parameters.

[0332] 79. An inkjet printing device as described in clause 78, wherein the quality parameters include the number of satellites formed and / or the roundness of the average features printed.

[0333] 80. An inkjet printing device as described in any one of clauses 75 to 79, wherein the parameter map is derived by using a look-up table.

[0334] 81. An inkjet printing device as described in any one of clauses 69 to 80, wherein the surface of the spectacle lens substrate is a curved surface.

[0335] 82. An inkjet printing device as described in any one of clauses 69 to 81, wherein the at least two printing nozzle groups are to be used within a single pass of printing.

[0336] 83. An inkjet printing device as described in any one of clauses 69 to 82, wherein the printing parameter values of at least one adjustable printing parameter for each printing nozzle group are determined individually such that it is not necessary to adjust the inclination angle of the print head relative to the surface of the spectacle lens substrate before and / or during printing.

[0337] 84. An inkjet printing device as described in any one of clauses 69 to 83, wherein the printing parameter values of at least one adjustable printing parameter for each printing nozzle group are determined individually such that during the printing of a pattern on the surface of the spectacle lens substrate, the postures of both the spectacle lens substrate and the print head remain unchanged relative to each other.

[0338] 85. A spectacle lens substrate having a pattern printed on the curved surface of the spectacle lens substrate obtainable by the method described in any one of clauses 65 to 68.

[0339] 86. A data set in the form of a computer-readable data carrier signal, the data set comprising at least one of the following types of data: (i) individual printing parameter values for at least one adjustable printing parameter of at least two printing nozzle groups of an inkjet printing device comprising a print head having a plurality of printing nozzles, the printing parameter values being configured to be fed into the inkjet printing device to print a pattern on the surface of a spectacle lens substrate; or (ii) data comprising computer-readable instructions for controlling the inkjet printing device to print a pattern on the surface of a spectacle lens substrate by applying the individual printing parameter values of at least one adjustable printing parameter to at least two printing nozzle groups of an inkjet printing device comprising a print head having a plurality of printing nozzles.

[0340] 87. The data set as described in clause 86, wherein the at least one adjustable printing parameter is selected from the group consisting of ejection temperature, ejection duration, ejection frequency, threshold value, waveform parameter, and adjustable ink properties.

[0341] 88. The data as described in clause 86 or clause 87, wherein each printing nozzle group comprises a single printing nozzle.

[0342] 89. The data set as described in any one of clauses 86 to 88, wherein the instructions cause the computer to obtain input data related to the geometric characteristics of the surface of the spectacle lens substrate and the print head, and wherein the computer is caused to determine the printing parameter values individually depending on the input data.

[0343] 90. The data set as described in clause 89, wherein the instructions cause a computer to use input data to determine a geometric relationship between the surface of the spectacle lens substrate and the print head, and wherein the geometric relationship is described by at least one parameter selected from the group consisting of a displacement vector, a velocity vector, an incident angle α, a distance Δ, or an arc length s.

[0344] 91. The data set as described in clause 89 or clause 90, wherein the input data includes data related to environmental conditions, non - adjustable ink properties, and / or material properties of the spectacle lens substrate.

[0345] 92. The data set as described in any one of clauses 86 to 91, wherein the instructions cause a computer to derive a parameter mapping that includes assigning print parameter values to a specific set of points on the surface of the spectacle lens substrate.

[0346] 93. The data set as described in clause 92 in combination with at least clause 84, wherein the instructions cause a computer to derive a parameter mapping by optimizing a cost function that applies to the correlation between parameters describing the geometric relationship between the surface of the spectacle lens substrate and the print head and adjustable print parameters.

[0347] 94. The data set as described in clause 93, wherein the optimization uses at least one method selected from the group consisting of the steepest gradient descent method, genetic algorithms, and machine learning.

[0348] 95. The data set as described in clause 93 or clause 94, wherein the cost function defines cost depending on quality parameters.

[0349] 96. The data set as described in clause 95, wherein the quality parameters include the number of satellites formed and / or the roundness of the average features printed.

[0350] 97. The data set as described in any one of clauses 92 to 96, wherein the parameter mapping is derived by using a look - up table.

[0351] 98. The non - transitory computer - readable storage medium as described in any one of clauses 86 to 97, wherein the surface of the spectacle lens substrate is a curved surface.

[0352] 99. The non - transitory computer - readable storage medium as described in any one of clauses 86 to 98, wherein the at least two print nozzle groups are to be used within a single pass of printing.

[0353] 100. A non - transitory computer - readable storage medium as described in any one of clauses 86 to 99, wherein the printing parameter values of at least one adjustable printing parameter for each printing nozzle group are determined separately such that it is not necessary to adjust the tilt angle of the print head relative to the surface of the spectacle lens substrate before and / or during printing.

[0354] 101. A non - transitory computer - readable storage medium as described in any one of clauses 86 to 100, wherein the printing parameter values of at least one adjustable printing parameter for each printing nozzle group are determined separately such that during the printing of a pattern on the surface of the spectacle lens substrate, the postures of both the spectacle lens substrate and the print head remain unchanged relative to each other.

[0355] 102. A data set in the form of a computer - readable data signal, the data set including at least one of the following types of data: (i) a virtual representation of a device as described in any one of clauses 69 to 84, the virtual representation being configured to be fed into one or more manufacturing machines to manufacture the device, or (ii) data containing computer - readable instructions for controlling one or more manufacturing machines to manufacture a device as described in any one of clauses 69 to 84.

[0356] List of reference numerals

[0357] 1 Printing parameter value

[0358] 2 Inkjet printing device

[0359] 3 Surface

[0360] 4 Spectacle lens substrate

[0361] 5 Print head

[0362] 6, 6a, 6b, 6c Printing nozzle

[0363] 7, 7a, 7b, 7c, 7d, 7e, 7f Printing parameter

[0364] 8, 8a, 8b, 8c, 8d Input data

[0365] 9 Ink

[0366] 10a, 10b, 10c, 10d, 10e Printing nozzle group

[0367] 11, 11a, 11b, 11c Parameters describing geometric relationships

[0368] 12 Parameter mapping

[0369] 13 Look - up table

[0370] 20 Processor

[0371] 21 Storage medium

[0372] 100 Method

[0373] 200 Data processing system

[0374] D Diameter

[0375] dx, dy, dz Discrete differences within the coordinate system used

[0376] j Jet vector

[0377] m Moving direction of the print head

[0378] n Normal vector

[0379] r True front curve

[0380] s Arc length

[0381] α Angle of incidence

[0382] Δ1, Δ2 Distances between the print nozzles and the substrate surface

[0383] S1 Obtain input data related to the geometric features of the surface of the spectacle lens substrate and the print head of the inkjet printing device

[0384] S2 Group a plurality of print nozzles into at least two print nozzle groups

[0385] S3 Individually determine the print parameter values of the adjustable print parameters for each print nozzle group

[0386] S4 Provide a look-up table and a cost function

[0387] S5 Apply and optimize the cost function

[0388] S6 Derive a parameter mapping

Claims

1. A computer-implemented method (100) for determining printing parameter values (1) for an inkjet printing device (2) for printing a pattern on a surface (3) of an ophthalmic lens substrate (4) including a curved surface, the inkjet printing device (2) comprising a print head (5) as a single component having a plurality of printing nozzles (6, 6a, 6b, 6c), characterized in that, The method comprises the following method steps: -(S2): Grouping the plurality of printing nozzles (6, 6a, 6b, 6c) into at least two printing nozzle groups (10a, 10b, 10c, 10d, 10e), and -(S3): Individually determining a printing parameter value (1) of at least one adjustable printing parameter (7, 7a, 7b, 7c, 7d, 7e, 7f) for each printing nozzle group (10a, 10b, 10c, 10d, 10e), wherein an inclination angle of the print head (5) relative to a surface (3) of the spectacle lens substrate (4) is not adjusted before printing and / or during printing.

2. The method (100) according to claim 1, characterized in that, The at least one adjustable printing parameter (7, 7a, 7b, 7c, 7d, 7e, 7f) is selected from the group consisting of ejection temperature, ejection duration, ejection frequency, fan value, waveform parameter, and adjustable ink property.

3. The method (100) according to claim 1 or claim 2, characterized in that, The at least two printing nozzle groups are to be used within a single pass of printing.

4. The method (100) according to claim 1 or claim 2, characterized in that, Each printing nozzle group (10a, 10b, 10c, 10d, 10e) comprises a single printing nozzle (6, 6a, 6b, 6c).

5. The method (100) according to claim 1 or claim 2, characterized in that, The method comprises: -(S1): Obtaining input data (8, 8a, 8b) related to geometric features of a surface (3) of the spectacle lens substrate (4) and geometric features of the print head (5), wherein the printing parameter value (1) is individually determined depending on the input data (8, 8a, 8b).

6. The method (100) according to claim 5, characterized in that, The input data is used to determine a geometric relationship between the surface (3) of the spectacle lens substrate (4) and the print head (5), wherein the printing parameter value (1) is individually determined based on the geometric relationship.

7. The method (100) according to claim 6, characterized in that, The term "geometric relationship" refers to the alignment of the print head and the spectacle lens substrate relative to each other.

8. The method (100) according to claim 6, wherein The geometric relationship is described by at least one parameter (11a, 11b, 11c) selected from the group consisting of a displacement vector, a velocity vector, an incident angle α, a distance Δ, and an arc length s.

9. The method (100) according to claim 7, characterized in that, The geometric relationship is described by at least one parameter (11a, 11b, 11c) selected from the group consisting of a displacement vector, a velocity vector, an incident angle α, a distance Δ, and an arc length s.

10. The method (100) according to claim 5, characterized in that, The input data (8, 8c, 8d) includes data related to environmental conditions, non-adjustable ink properties, and / or material properties of the spectacle lens substrate (4).

11. The method (100) according to claim 6, characterized in that, The input data (8, 8c, 8d) includes data related to environmental conditions, non-adjustable ink properties, and / or material properties of the spectacle lens substrate (4).

12. The method (100) according to claim 7, wherein, The input data (8, 8c, 8d) includes data related to environmental conditions, non-adjustable ink properties, and / or material properties of the spectacle lens substrate (4).

13. The method (100) according to claim 8, characterized in that, The input data (8, 8c, 8d) includes data related to environmental conditions, non-adjustable ink properties, and / or material properties of the spectacle lens substrate (4).

14. The method (100) according to claim 1 or claim 2, characterized in that, The method step (S3) of individually determining the printing parameter value (1) of the at least one adjustable printing parameter (7, 7a, 7b, 7c, 7d, 7e, 7f) includes deriving a parameter map (12) (S6), the parameter map including an assignment of the printing parameter value (1) to a specific group of data points on the surface (3) of the spectacle lens substrate (4).

15. The method (100) according to claim 6, wherein The method step (S3) of individually determining the printing parameter value (1) of the at least one adjustable printing parameter (7, 7a, 7b, 7c, 7d, 7e, 7f) includes deriving a parameter map (12) (S6), which includes assigning the printing parameter value (1) to a specific group of data points on the surface (3) of the spectacle lens substrate (4).

16. The method (100) according to claim 14, wherein Deriving the parameter map (12) includes converting the surface (3) of the spectacle lens substrate (4) into a grid of data points.

17. The method (100) according to claim 6, characterized in that, The method step (S3) of individually determining the printing parameter value (1) of the at least one adjustable printing parameter (7, 7a, 7b, 7c, 7d, 7e, 7f) includes providing a look-up table that includes the correlation between the parameters (11a, 11b, 11c) describing the geometric relationship between the surface (3) of the spectacle lens substrate (4) and the print head and the printing parameter value (1) of the adjustable printing parameter (7, 7a, 7b, 7c, 7d, 7e, 7f).

18. The method (100) according to claim 16, characterized in that, The method step (S3) of individually determining the printing parameter value (1) of the at least one adjustable printing parameter (7, 7a, 7b, 7c, 7d, 7e, 7f) includes providing a look-up table that includes the correlation between the parameters (11a, 11b, 11c) describing the geometric relationship between the surface (3) of the spectacle lens substrate (4) and the print head and the printing parameter value (1) of the adjustable printing parameter (7, 7a, 7b, 7c, 7d, 7e, 7f).

19. The method (100) according to claim 18, characterized in that, Individually determining these printing parameter values (1) includes deriving a set of printing parameter values from the look-up table of these data points.

20. The method (100) according to claim 15, characterized in that, The parameter map (12) is derived by optimizing a cost function (S5), which is applied to the correlation between the parameters (11a, 11b, 11c) describing the geometric relationship between the surface (3) of the spectacle lens substrate (4) and the print head (5) and the printing parameter value (1) of the adjustable printing parameter (7, 7a, 7b, 7c, 7d, 7e, 7f).

21. The method (100) according to claim 1 or claim 2, characterized in that, Individually determining the printing parameter value (1) of the at least one adjustable printing parameter (7, 7a, 7b, 7c, 7d, 7e, 7f) for each print nozzle group (10a, 10b, 10c, 10d, 10e) such that it is not necessary to adjust the tilt angle of the print head (5) relative to the surface (3) of the spectacle lens substrate (4) before and / or during printing.

22. A data processing system (200), the data processing system including a processor (20) and a storage medium (21) coupled to the processor (20), wherein, The processor (20) is adapted to determine a print parameter value (1) for an inkjet printing device (2) for printing a pattern on a surface (3) of an ophthalmic lens substrate (4) comprising a curved surface, based on a computer program stored on the storage medium (21), the inkjet printing device (2) comprising a print head (5) as a single component having a plurality of print nozzles (6, 6a, 6b, 6c), characterized in that the processor (20) is adapted to group the plurality of print nozzles (6, 6a, 6b, 6c) into at least two print nozzle groups (10a, 10b, 10c, 10d, 10e), and to individually determine a print parameter value (1) of at least one adjustable print parameter (7, 7a, 7b, 7c, 7d, 7e, 7f) for each print nozzle group (10a, 10b, 10c, 10d, 10e), wherein an inclination angle of the print head (5) relative to the surface (3) of the ophthalmic lens substrate (4) is not adjusted before and / or during printing.

23. The data processing system (200) according to claim 22, wherein The processor (20) is adapted to individually determine the print parameter value (1) depending on geometric features of the ophthalmic lens substrate (4) and geometric features of the print head (5).

24. A computer program product having a computer program which includes instructions that, when executed by a computer, cause the computer to determine values of printing parameters for an inkjet printing device (2) for printing a pattern on a surface (3) of an ophthalmic lens substrate (4) including a curved surface, the inkjet printing device (2) including a print head (5) as a single component having a plurality of printing nozzles (6, 6a, 6b, 6c), characterized in that, The instructions cause the computer to group the plurality of print nozzles (6, 6a, 6b, 6c) into at least two print nozzle groups (10a, 10b, 10c, 10d, 10e), and to individually determine a print parameter value (1) of at least one adjustable print parameter (7, 7a, 7b, 7c, 7d, 7e, 7f) for each print nozzle group (10a, 10b, 10c, 10d, 10e), wherein an inclination angle of the print head (5) relative to the surface (3) of the ophthalmic lens substrate (4) is not adjusted before and / or during printing.

25. A non-transitory computer-readable storage medium comprising instructions that, when executed by a computer, cause the computer to determine print parameter values (1) for an inkjet printing device (2) for printing a pattern on a surface (3) of an ophthalmic lens substrate (4) including a curved surface, the inkjet printing device (2) including a print head (5) as a single unit having a plurality of print nozzles (6, 6a, 6b, 6c), characterized in that, The instructions cause the computer to group the plurality of print nozzles (6, 6a, 6b, 6c) into at least two print nozzle groups (10a, 10b, 10c, 10d, 10e), and to individually determine a print parameter value of at least one adjustable print parameter (7, 7a, 7b, 7c, 7d, 7e, 7f) for each print nozzle group (10a, 10b, 10c, 10d, 10e), wherein an inclination angle of the print head (5) relative to the surface (3) of the ophthalmic lens substrate (4) is not adjusted before and / or during printing.

26. A method for inkjet printing, wherein, Printing a pattern on a surface (3) of an ophthalmic lens substrate (4) comprising a curved surface using a print parameter value (1) of at least one adjustable print parameter (7, 7a, 7b, 7c, 7d, 7e, 7f) with an inkjet printing device (2) comprising a print head (5) as a single component having a plurality of print nozzles (6, 6a, 6b, 6c), characterized in that the print parameter value (1) of the at least one adjustable print parameter (7, 7a, 7b, 7c, 7d, 7e, 7f) is determined according to the computer-implemented method according to any one of claims 1 to 21.

27. An inkjet printing device (2) for printing a pattern on a surface (3) of an ophthalmic lens substrate (4) including a curved surface, the inkjet printing device (2) comprising: - a printhead (5) as a single component having a plurality of printing nozzles (6, 6a, 6b, 6c), and - a data processing system (200) including a processor (20) and a storage medium (21) coupled to the processor (20), wherein the processor (20) is adapted to determine a printing parameter value (1) based on a computer program stored on the storage medium (21), characterized in that the processor (20) is adapted to group the plurality of printing nozzles (6, 6a, 6b, 6c) into at least two printing nozzle groups (10a, 10b, 10c, 10d, 10e), and separately determine the printing parameter value (1) of at least one adjustable printing parameter (7, 7a, 7b, 7c, 7d, 7e, 7f) for each printing nozzle group (10a, 10b, 10c, 10d, 10e), wherein the inclination angle of the printhead (5) relative to the surface (3) of the ophthalmic lens substrate (4) is not adjusted before and / or during printing.

28. A computer-readable storage medium having a data set stored thereon, the data set including at least one of the following types of data: (i) a virtual representation of the device according to claim 27, the virtual representation being configured to be fed into one or more manufacturing machines to manufacture the device, or (ii) data containing computer-readable instructions for controlling one or more manufacturing machines to manufacture the device according to claim 27.

29. A computer-readable storage medium having a data set stored thereon, the data set including at least one of the following types of data: (i) individual print parameter values (1) for at least one adjustable print parameter (7, 7a, 7b, 7c, 7d, 7e, 7f) of a print nozzle group (10a, 10b, 10c, 10d, 10e) for an inkjet printing device (2) including a print head (5) having a plurality of print nozzles (6, 6a, 6b, 6c), the print parameter values being configured to be fed into the inkjet printing device (2) to print a pattern on a surface (3) of an ophthalmic lens substrate (4), the ophthalmic lens substrate including a curved surface, wherein, The inclination angle of the printhead (5) relative to the surface (3) of the ophthalmic lens substrate (4) is not adjusted before and / or during printing; or (ii) data containing computer-readable instructions for controlling the inkjet printing device (2) to print a pattern on a surface (3) of an ophthalmic lens substrate (4) including a curved surface by applying the separate printing parameter values (1) of at least one adjustable printing parameter (7, 7a, 7b, 7c, 7d, 7e, 7f) to at least two printing nozzle groups (10a, 10b, 10c, 10d, 10e) of the inkjet printing device (2) having a plurality of printing nozzles (6, 6a, 6b, 6c) as a single component, wherein the inclination angle of the printhead (5) relative to the surface (3) of the ophthalmic lens substrate (4) is not adjusted before and / or during printing.

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