METHOD FOR APPLYING A MARKING ON AN OBJECT AND MARKING APPARATUS

Abstract

The invention relates to a method for applying a marking within a marking area on an object, in which at least one light beam is emitted with light emitting means, scanning means are moved to deflect the light beam line by line over the marking area, while the light emitting means is switched between being activated or deactivated according to the marking to be applied. The method is characterized in that, for each start of a line movement of the light beam over the object, the scanning means is moved such that its deflection direction points at a line starting point outside the marking area and the scanning means is accelerated such that its deflection direction is accelerated from the line starting point towards the marking area, wherein the light emitting means is deactivated while the deflection direction points somewhere outside the marking area. The invention further relates to a corresponding marking apparatus.

Claims

1. A method for applying a marking (1) within a marking area (10) on an object (30), in which at least one light beam (27) is emitted with light emitting means (23), scanning means (25) are moved to deflect the light beam (27) line by line over the marking area (10), while the light emitting means (23) is switched between being activated or deactivated according to the marking (1) to be applied, characterized in that for each start of a line movement of the light beam (27) over the object (30), the scanning means (25) is moved such that its deflection direction points at a line starting point (11) outside the marking area (10) and the scanning means (25) is accelerated such that its deflection direction is accelerated from the line starting point (11) towards the marking area (10), wherein the light emitting means (23) is deactivated while the deflection direction points somewhere outside the marking area (10).

2. The method according to claim 1, characterized in that the deflection direction is moved with the scanning means (25) with a constant speed within the marking area (10).

3. The method according to claim 2, characterized in that the constant speed of the deflection direction is set by a constant rotational speed of the scanning means (25).

4. The method according to claim 1, characterized in that for each line movement of the deflection direction, it is accelerated from the respective line starting point (11) until the start of marking area (10), from where the deflection direction is further moved with a constant speed.

5. The method according to claim 1, characterized in that an acceleration of a movement of the deflection direction becomes smaller while the deflection direction moves from the line starting point (11) to the marking area (10).

6. The method according to claim 1, characterized in that one raw image line to be marked is represented by several neighboring lines of the line by line movement of the deflection direction.

7. The method according to claim 1, characterized in that from raw image data, several image line vectors are derived, each image line vector being constituted of a string of first pixel values for which the light emitting means (23) are activated and second pixel values for which the light emitting means (23) are deactivated, the movement of the scanning means (25) is determined via the lengths and number of the image line vectors, for controlling the scanning means (25) to move its deflection direction not merely over the marking area but to start at the respective line starting point (11), a dummy vector is added to the image line vector, the dummy vector being constituted of only second pixel values.

8. The method according to claim 1, characterized in that in the line by line movement of the deflection direction, directly neighboring lines have antiparallel movement directions, for compensating a displacement between directly neighboring lines due to the acceleration of the deflection direction leading to a mark for the respective line being shifted towards its respective line starting point, every second line is displaced by a common adjustable amount.

9. The method according to claim 8, characterized in that for determining a value for the common adjustable amount, the following steps are carried out: a reference marking is produced, the reference marking is analyzed to determine the displacement between directly neighboring lines, the common adjustable amount is set dependent on the determined displacement.

10. The method according to claim 1, characterized in that a transverse movement of the deflection direction for shifting to a next line is carried out during an acceleration phase of the deflection direction between the line starting point (11) and the beginning of the marking area (10), and/or during a deceleration phase after leaving the marking area (10).

11. The method according to claim 1, characterized in that a plurality of light beams is directed simultaneously onto the scanning means (25) to simultaneously produce several line marks.

12. The method according to claim 1, characterized in that dependent on a raw image to be marked, some raw image lines start with a first pixel value for which the light emitting means are to be activated, and others start with a second pixel value for which the light emitting means are to be deactivated, leading to some lines within the marking area (10) starting with an unmarked region (3) corresponding to a second pixel value, and other lines within the marking area starting with a marked region (2) corresponding to a first pixel value, the line starting points (11) of different lines are determined as one fixed distance before a first region to be marked (2) within the marking area (11), the first region (2) corresponding to a 1.sup.st first pixel value of that line, leading to the line starting points (11) having different positions with regard to a line movement direction dependent on the position of the 1.sup.st first pixel value of that line.

13. A marking apparatus for applying a marking (1) within a marking area (10) on an object (30), comprising light emitting means (23) for emitting at least one light beam (27) used for marking, scanning means (25) for deflecting the light beam (27), control means (20) for moving the scanning means (25) to deflect the light beam (27) line by line over the marking area (10) while switching the light emitting means (23) between being activated or deactivated according to the marking (10) to be applied, characterized in that the control means (20) is adapted to move the scanning means (25), for each start of a line movement of the light beam (27) over the object (30), such that a deflection direction of the scanning means (25) points at a line starting point (11) outside the marking area (10) and to accelerate the scanning means (25) such that its deflection direction is accelerated from the line starting point (11) towards the marking area (10), and to deactivate the light emitting means (23) while the deflection direction points somewhere outside the marking area (10).

14. The marking apparatus according to claim 13, characterized in that the scanning means (25) comprise at least two deflection elements, in particular mirrors, that can be rotated about different axes, and the two deflection elements are jointly controlled to create the line by line movement.

Description

[0059] A better understanding of the invention and various other features and advantages of the present invention will become readily apparent by the following description in connection with the schematic drawings, which are shown by way of example only, and not limitation, wherein like reference numerals may refer to alike or substantially alike components:

[0060] FIG. 1 shows a marking produced with a related art method;

[0061] FIG. 2 shows an enlarged portion of FIG. 1;

[0062] FIG. 3 shows a further marking;

[0063] FIG. 4 shows a detail of FIG. 3;

[0064] FIG. 5 shows a diagram of how to move a light beam with scanning means, for illumination a part of the inventive marking method and apparatus;

[0065] FIG. 6 shows an explanatory diagram of a marking to be produced;

[0066] FIG. 7 shows a sequence of method steps of an embodiment of an inventive method;

[0067] FIG. 8 shows a sequence of method steps of another embodiment of an inventive method; and

[0068] FIG. 9 shows an embodiment of an inventive apparatus.

[0069] A related art marking method is shown in FIGS. 1 and 2. This method is described in the introductory portion of this application and shows several disadvantages compared to the method of the invention: First, the marking method of FIGS. 1 and 2 is not capable of very high marking speeds. Furthermore, a vibration of e.g. the object leads to a shift of the marking part that is produced during the vibration relative to the remaining marking parts, deteriorating readability.

[0070] A generic marking method uses a line by line scanning sequence which leads to the marking shown in FIG. 3. This marking is described in the introductory part and can be produced either with an inventive or a related art method.

[0071] A detail of FIG. 3 in shown in FIG. 4 for explanation of an embodiment of the inventive marking method. Each pixel of an image or raw image to be marked corresponds in position to one cell 2, 3 within a marking area on the object. A mark in one cell 2 is here not produced by moving the light beam once over that cell 2. Rather, several line movements 6 of the light beam cross one cell 2. In the depicted example, three line movements 6 lead through each cell 2, 3. Light beams with small cross sections can thus be used. This improves image quality, and, as light intensity is not equally distributed throughout the light beam cross section, multiple small cross section lines avoid one large beam with a problematically high light intensity at its centre.

[0072] To minimize the required marking time, consecutive lines are scanned in antiparallel directions, as shown with the arrows 6.

[0073] A main aspect of the invention resides in the control of scanning means for deflecting the light beam. This movement is best described with an impinging spot, i.e., an area on the object onto which a light beam is or would be deflected with the scanning means. The impinging spot is moved via the scanning means over the object.

[0074] For producing the single marks that make up the marking, prior art methods merely move the impinging spot within the marking area, i.e. from one region where a mark is to be created to the next region where a mark is to be created.

[0075] In contrast, the inventive method demands the impinging spot to be moved outside the marking area. This leaves room for accelerating the scanning means before the marking process begins. From then on, a constant speed of the scanning means can be deployed. Overall, this reduces the required marking time.

[0076] This concept will be further described with reference to FIG. 5. The upper part of this figure shows the beginning of one line movement of the impinging spot, i.e. the deflection direction of the scanning means. Below the speed with which the impinging spot is scanned over the object is shown.

[0077] The marking process starts with moving the impinging spot to a line starting point 11, shown as a dotted circle in FIG. 5. From there, the scanning means is accelerated, leading to an accelerating movement of the impinging spot in the direction 6. The line starting point 11 is chosen at a position outside a marking area 10 in which the marking is to be produced. The acceleration of the impinging spot movement ends upon reaching the marking area 10, as shown with the speed function 24 which is depicted in a diagram of speed v against the space coordinate x in the lower part of FIG. 5.

[0078] The light emitting means is deactivated while the impinging spot is outside the marking area 10.

[0079] During the line movement within the marking area 10, the light emitting means are alternatingly activated and deactivated, according to image data. In this way, several marks 2 separated by blank regions 3 are formed. Within the marking area 10, the impinging spot is moved with a constant speed, as shown by the speed function 24. In this way, no waiting times after a jump, i.e. after passing over a blank region 3, are required, and hence time can be saved as compared with prior art techniques.

[0080] The line starting point 11 is chosen as a fixed distance in front of the marking area 10. This distance should not be too large as this would again lead to an increase in time demand. It is preferable that the line starting point 11 is set dependent on the position of a first pixel in one line which requires the light emitting means to be turned on. This will be illuminated with reference to FIG. 6.

[0081] FIG. 6 shows a marking 1 as well as arrows 7, 8a, 8b, 8c and 8d which indicate the line movement outside the marking area. A scanning or line movement direction is alternatingly from left to right and from right to left. Note that each image line corresponds to several neighbouring line marks, e.g. a lowest image line corresponds to a first line movement from left to right, followed by a movement from right to left according to the arrow 8d, which jointly produce the depicted sequence of filled cells 2.

[0082] A line starting point is indicated in FIG. 6 as the beginning of a respective arrow 7 and 8a to 8d. On the left side of the marking 1, the first cell 2 to be filled, i.e. the first mark in each cell, is located at the same position with regard to the line movement direction. Consequently, all line starting points on the left side are at the same position with regard to the line movement direction. In contrast, on the right side of the marking 1, the first cell 2 to be filled varies with different lines. The line starting points on the right side are chosen accordingly: The arrows 8a to 8d start at different positions in the line movement direction, such that a common distance is formed from a line starting point to its respective first cell 2 to be filled in the respective line.

[0083] A problem related with the introduction of the inventive acceleration phase as well as its solution according to a variant of the invention will be described with reference to FIGS. 7 and 8.

[0084] FIG. 7 shows several line movements of the deflection direction of the scanning means as well as the marks 2 thus produced. To begin the marking process, the deflection direction, i.e. the impinging spot onto which the deflection direction points, is moved to the line starting point 11a, as indicated with arrow 13a. From here, the impinging spot is accelerated towards the marking area, then the light emitting means are activated several times to form marks 2, and when the end of the marking area is reached, the impinging spot is decelerated and moved to a line starting point 11b of a next line, as indicated with arrow 13b.

[0085] From the line starting point 11b, a procedure similar to the one explained above follows; the difference being that this line is scanned from right to left instead of left to right. These directions should be understood as merely being opposite each other, and are thus equivalent to a “top to bottom direction” or any differently orientated pair of antiparallel movements.

[0086] The scanning movement continues after the second line to the line starting point 11c of the third line, and so forth.

[0087] The position of the line starting points 11a to 11d can be expressed via dummy vectors that are added to image data line vectors according to which one line of the marking 1 is to be produced. The length of a dummy vector influences the distance 14 from a line starting point to the marking area.

[0088] The movement of the impinging spot during the acceleration phase of each line is comparably slow. Without counter measures being taken, this leads to the entries of the dummy vector being translated to smaller distances on the object than the entries of the image data line vectors which encode the image to be marked. The marks 2 of each line are thus displaced towards the line starting point 11a to 11d of the respective line. This leads to a displacement 15 between marks 2 of lines that are scanned from right, and marks 2 of lines that are scanned from left.

[0089] The displacement 15 constitutes a distortion of the marking 1 and should be compensated. This is achieved with an embodiment of the invention that will be described with reference to FIG. 8.

[0090] FIG. 8 differs from FIG. 7 in that a compensating displacement 16 is added to all line movements that start from the left side. That is, the line starting points 11a and 11c do not start at the positions of FIG. 7 (indicated in FIG. 8 by hollow circles) but at a position displaced in the line movement direction by a common amount. Depending on the technical implementation, this may be achieved with a different length of a dummy vector for lines scanned from left compared to lines scanned from right.

[0091] Naturally, a compensating displacement may instead or additionally be applied to the lines scanned from right.

[0092] A marking apparatus 100 for carrying out the described method is shown in FIG. 9. The marking apparatus 100 comprises light emitting means 23, such as one or more lasers, for emitting one or more light beams 27, scanning means 25 to variably deflect the light beam 27, and electronic control means 20 to control the light emission and deflection. The light beam 1 is guided onto a surface of an object 30 to produce a marking 1.

[0093] The control means 20 are adapted to automatically execute the above-described method after input of image data or other print instructions.

[0094] In this way, a marking can be produced particularly fast without affecting the marking quality.