The present invention relates to a method for printing a three-dimensional optical component with an inkjet printer, wherein the three-dimensional component is built up from layers of printing ink through a targeted placement of droplets of printing ink at least partially side by side and one above the other in successive printing steps.
Printing three-dimensional optical components such as lenses, mirrors and the like is known from the prior art. The optical structures are built up layer by layer through a targeted placement of droplets of printing ink. The droplets are ejected towards a substrate by ejection nozzles of the print head of an inkjet printer. Through clogging or other technical defects, individual ejection nozzles may be inoperative or malfunctioning, resulting in a print of poor quality. To circumvent these and other printing errors, properties of the printed structure may be determined, identified and corrected immediately during the printing process.
Suchlike methods suffer from the drawback that they are either time consuming or involve costly equipment, resulting in longer printing cycles and higher printing costs.
It is a purpose of the present invention to provide a method for printing an optical three-dimensional component of high accuracy in a fast, efficient and costly manner as compared to methods known from the prior art. High accuracy in the print not only of the shape of the final structure, but also of its internal layered structure is particularly important for optical components as the internal structure determines the optical properties of the resulting component.
According to the present invention, this object is achieved by a method for printing a three-dimensional optical component with an inkjet printer, wherein the three-dimensional component is built up from layers of printing ink through a targeted placement of droplets of printing ink at least partially side by side and one above the other in successive printing steps, characterized in that at least one printing step is followed by a first scanning step during which surface properties of the two-dimensional surface defined by the last printed layer are determined through a one-dimensional measurement along a first direction by a measurement means, a rotation step during which the structure built up in the preceding steps is rotated with respect to the measurement means by a defined rotation angle and a second scanning step during which surface properties of the two-dimensional surface are determined through a one-dimensional measurement along a second direction by the measurement means. Preferably, the structure is rotated around an axis of rotation in the rotation step, wherein the axis of rotation is arranged perpendicular to a main extension plane of the two-dimensional surface defined by the last printed layer.
Herewith it is advantageously possible to detect printing errors directly during the printing process in a fast, efficient and cost-effective manner. In particular, the described method allows to infer deviations of the two-dimensional surface from its intended shape from two consecutive, one-dimensional measurements. This saves time and costs, as two-dimensional scans of the surface become superfluous. Likewise, costly equipment necessary to carry out measurements of the full two-dimensional surface is spared.
In the sense of the present invention, printed structure comprises the final three-dimensional optical component as well as all intermediates obtained during the printing process.
Preferably, wherein the first direction is the printing direction, i.e. the direction defined by the relative movement of a print head of the inkjet printer with respect to the printed structure and the rotation angle is 90°.
The one-dimensional measurement preferably comprises determination of the height profile of the two-dimensional surface along the first and second direction, respectively. The corresponding measurement means may be a line sensor. This has the advantage that the one-dimensional measurement along a first or second direction on the surface can be carried out in a single instance. Unfortunately, line sensors are costly. Therefore, the measurement means comprises a point sensor relative to which the printed structure is moved along the first and the second direction, respectively, in a preferred embodiment. In this way, identical information can be captured at a reduced production cost.
Another object of the present invention is a method for printing a three-dimensional optical component with an inkjet printer, wherein the three-dimensional structure is built up from layers of printing ink through a targeted placement of droplets of printing ink at least partially side by side and one above the other in successive printing steps, wherein at least one printing step is followed by a scanning step during which surface properties of the two-dimensional surface defined by the last printed layer are determined through a one-dimensional measurement by a measurement means, characterized in that the printed structure is rotated relative to the measurement means while the measurement is carried out. Preferably, the structure is rotated around an axis of rotation, wherein the axis of rotation is arranged perpendicular to a main extension plane of the two-dimensional surface defined by the last printed layer.
This advantageously provides an alternative method for detecting printing errors directly during the printing process in a fast, efficient and cost-effective manner, relying on measurement means apt at line- or pointwise measurements only.
The one-dimensional measurement comprises, e.g., determination of the height profile of the two-dimensional surface along at least one direction.
In a preferred embodiment, the printed structure is additionally moved relative to the measurement means in a direction perpendicular to the axis of rotation. Preferably, the printed structure is moved radially inwards in a first linear movement and then radially outwards in a second linear movement relative to the measurement means. Using a measurement means which comprises a point sensor, the entire surface of the printed structure can thus can scanned along a spiral path. Alternatively, the measurement means may comprise a line sensor.
Any of the previously described methods profits from tilting the measurement means with respect to the printed structure during the measurement, in order to avoid unfavorable reflection angles during measurement.
Another object of the present invention is a printer for carrying out a method as previously described. In particular, the printer comprises a print head, a printing plate, a measurement means and a motor, which drives a relative rotation of the printing plate with respect to the measurement means. In line with the above described methods, the measurement means preferably comprises a line sensor or a point sensor. The measurement means may additionally and preferably comprise a tilting device for adjusting the measurement angle to the height and shape of the printed structure. Preferably, the rotation is a rotation around an axis of rotation, wherein the axis of rotation is arranged perpendicular to the printing plate.
Herewith a printer is provided that allows printing of three-dimensional optical components with the benefits and advantages of the above described methods.
The present invention will be described with respect to particular embodiments and with target to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and for illustrative purposes may not be drawn to scale.
Where an indefinite or definite article is used when referring to a singular noun, e.g. “a”, “an”, “the”, this includes a plural of that noun unless something else is specifically stated.
Furthermore, the terms first, second, third and the like in the description and in the claims are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.
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Preferably, the measurement results from the first and second scanning steps are analysed and converted into an error map. The error map contains information on the measured deviations of the layer 10. The remaining printing process is preferably determined by this information. E.g. the printing may be halted and the structure 2 printed so far may be discarded. Preferably, this is the case if the deviations cannot be healed or corrected by further printing or curing steps. Alternatively, the error map is preferably superimposed on the printing data. The updated printing data account for the measured errors such that these are corrected through the following printing steps. The correction of errors is preferably obtained over a number of printing steps and not in a single step as otherwise optical deficiencies may result. Preferably, the error cancelation involves ten successive layers 10. In this way, a method is advantageously provided that allows a fast, efficient and cost-effective measurement step, ensuring high quality of the resulting optical structure 2. In particular, the high accuracy in the layered structure necessary for the printing of three-dimensional optical components 2 is achieved.
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Number | Date | Country | Kind |
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19158359.0 | Feb 2019 | EP | regional |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2020/054401 | 2/19/2020 | WO | 00 |