LIQUID CRYSTAL DISPLAY FOR LASER MARKER

Abstract: A liquid crystal display for a laser marker for attaining a higher marking speed, characterized in that a liquid crystal display screen (10) is divided into a first zone (10a) where a sub-scanning is first performed and a second zone (10b) where a sub-scanning is performed following the first zone (10a) sub-scanning, that switching of display is performed independently for each of the first and second zones (10a,10b), and predetermined voltages are applied, respectively, to row and column electrodes after those row and column electrodes are grounded, whereby display switching processing can be performed independently for each of the first and second zones. Completion of the sub-scanning of the first zone (10a) is detected by a position detecting means, and when such a detection is done, switching of display in the first zone (10a) is independently performed. In addition, when the position detecting means detects the completion of sub-scanning of the second zone (10b), switching of display in the second zone (10b) is performed independently.

Description: The present invention relates to systems for displaying a pattern on a liquid crystal for a laser marker and more particularly, to a system for performing predetermined control over switching of display to attain high speed marking. For a technique for applying liquid crystal made from so-called high polymer compound to a mask for a laser marker, the applicant of the present application has already filed patent applications (Japanese Patent Application No. 2-268 988 etc.). In such a high polymer compound type liquid crystal, when it is desired to switch the display screen of the liquid crystal, i.e., a marking pattern, this is attained, for the purpose of preventing from an after-image at the time of the switching of display, by performing such nondisplay processing that grounds row and column electrodes provided for the respective pixels of the liquid crystal and then by applying predetermined voltages to the row and column electrodes. In this case, ones of the pixels subjected to no application of such voltages are put in their laser-beam scattering state while the other pixels subjected to the application of the voltages are put in their laser-beam transmission state. However, the above display switching operation is not instantaneously carried out and requires a time of about 60 msec. Accordingly, during this display switching time, the liquid crystal is put in its non-display state and the marking is not performed, hence this time period becomes a wasteful time in operation. In addition, such switching of the display screen is generally continually done and pattern marking operation is often continuously done. In this case, since the above switching time is required whenever the pattern is changed, such switching time is accumulated for each pattern change to reach a lot of loss time when viewed from the entire operation, which hinders realization of high-speed marking. An invention for realizing high-speed marking is disclosed, for example, in Japanese Patent Application Laid-Open Publication No. 2-268988, in which the display surface of a liquid crystal mask for a laser marker is divided into 2 upper and lower sections so that, when scanning for the upper half is completed and then scanning starts for the lower half, rewriting is carried out for a marking pattern of the upper half. This invention, however, fails to positively describe such processing as to put only the upper half display in its non-display state during the display switching operation of the upper half display. Therefore, when the invention is applied to a laser marker with use of the aforementioned high polymer compound type liquid crystal as it is, this disadvantageously involves generation of an after-image. When analyzed, the liquid crystal switching time is roughly divided into a time necessary for extinguishing the pattern being displayed and a time necessary for activating a new display pattern. Between these times, the displayed-pattern extinguishment time, which depends on the composition material, structure, etc. of the liquid crystal mask, cannot be easily shortened. For this reason, for the purpose of realizing high-speed marking, when the marking operation is started before the liquid crystal display appears, irregularities take place in the marking on a workpiece. Accordingly, there has been a limit in realizing higher-speed marking while maintaining the marking quality. In view of such circumstances as mentioned above, it is a first object of the present invention to realize high-speed marking for a laser marker with use of, in particular, a high polymer compound type liquid crystal while preventing generation of an after-image. A second object of the present invention is to attain high-speed marking while maintaining the marking quality. These objects are solved by a liquid crystal display according to claim 1. In a liquid crystal display for a laser marker row and column electrodes are provided for each of pixels of a liquid crystal, wherein the row and column electrodes are grounded and then predetermined voltages are applied to the row and column electrodes to perform switching of display of a liquid crystal display screen. A laser beam is irradiated on the liquid crystal display screen and scanned on the liquid crystal display screen to mark a predetermined pattern displayed on the liquid crystal display screen onto a target object. The liquid crystal display comprises a display switching means for dividing the liquid crystal display screen into a first zone to be firstly subjected to a sub-scanning operation and a second zone to be subjected to a sub-scanning operation following the first zone, for performing switching operation of the display over the first and second zones independently of each other, a position detecting means for detecting a position of the liquid crystal display screen at which the sub-scanning is being presently carried out and a means for controlling the display switching means to perform switching operation of display of the first zone when the position detecting means detects completion of the sub-scanning of the first zone and to perform switching operation of display of the second zone when the position detecting means detects completion of the sub-scanning of the second zone. According to the invention, the display switching means is arranged for grounding the row and column electrodes of the first zone whilst the predetermined voltages are applied to the row and column electrodes of the second zone With such an arrangement, the liquid crystal display screen is divided into the first zone to be firstly subjected to the sub-scanning operation and the second zone to be subjected to the sub-scanning operation following the first zone, switching operation of the display is performed over the first and second zones independently of each other, and the row and column electrodes are grounded and then the predetermined voltages are applied to the row and column electrodes. The completion of the sub-scanning of the first zone is detected by the position detecting means, at which time the switching of display of the first zone is independently carried out. The completion of the sub-scanning of the second zone is detected by the position detecting means, at which time the switching of display of the second zone is independently carried out. Fig. 1 shows an arrangement of a liquid crystal display screen switching system for a laser marker in accordance with an embodiment of the present invention; Fig. 2 is a diagram for explaining how a laser beam scans a liquid crystal display screen shown in Fig. 1; Fig. 3 is a diagram for explaining an arrangement of a liquid crystal mask shown in Fig. 1; Fig. 4 shows a timing chart for explaining the operation of the system of Fig. 1; Fig. 5 shows an example of a pattern marked through the system of Fig. 1; Fig. 6 shows a timing chart for explaining the operation based on a prior art laser marker; A preferred embodiment of a liquid crystal display for a laser marker in accordance with the present invention will be explained with reference to the accompanying drawings. Fig. 1 conceptionally shows an arrangement of a laser marker in the preferred embodiment. In the drawing, a laser oscillator 1 oscillates to issue a scanning laser beam (such as a YAG (yttrium aluminum garnet) laser beam), which oscillated laser beam is irradiated on a reflective surface 2a of a deflector 2. A laser beam reflected by the reflective surface 2a is illuminated or irradiated on a reflective surface 3a of a deflector 3 made in the form of a polygon mirror through a lens 4. The laser beam reflected from the reflective surface 3a is illuminated or irradiated on a liquid crystal display screen 10 of a high polymer compound type liquid crystal mask 6 via a lens 5. The reflective surface 2a of the deflector 2 is rotated in a direction shown by an arrow AA by a motor 8, and the reflective surface 3a of the deflector 3 is rotated in a direction shown by an arrow BB by a motor 9. Accordingly, when the drive control of the motor 9 causes rotation of the reflective surface 3a in the arrow BB direction, the laser beam main-scans the liquid crystal display screen 10 of the liquid crystal mask 6 in a direction shown by an arrow X; while, when the drive control of the motor 8 causes rotation of the reflective surface 2a in the arrow AA direction, the laser beam sub-scans the liquid crystal display screen 10 of the liquid crystal mask 6 in a direction shown by an arrow Y. The manner the laser beam scans the liquid crystal display screen 10 is shown by arrows in Fig. 2. A controller 7 controls the driving operations of the above motors 8 and 9, controls the laser oscillation of the laser oscillator 1, and outputs a signal for driving the pixels of the liquid crystal display screen 10 of the liquid crystal mask 6. The controller 7, on the basis of information on a marking pattern entered through a predetermined input means, outputs a signal for driving associated ones of the pixels of the liquid crystal display screen 10 of the liquid crystal mask 6 corresponding to the pattern. In response to this, the associated pixels on the liquid crystal display screen 10 of the liquid crystal mask 6 are driven. Then the control of the driving operations of the motors 8 and 9 as well as the control of the operation of the laser oscillator 1 cause a laser beam to be scanned so that the laser beam transmits only the driven pixels and passes through a predetermined optical system (not shown), whereby a character, figure, etc. corresponding to a shape (the shape of the marking pattern) of the driven pixels are marked, e.g., on a surface of such a work 13 as shown in Fig. 5. More specifically, as shown in Fig. 5, a pattern 14 to be marked is divided into a plurality of marking patterns of blocks A to L so that the system of the present embodiment performs sequential marking operation over the respective marking patterns of the blocks. Accordingly, it is necessary to sequentially switch the pixel to be driven on the liquid crystal display screen 10 on a block basis of the blocks A to L. Shown in Fig. 3 is details of an arrangement of the liquid crystal mask 6 in which the liquid crystal display screen 10 is made up of pixels arranged in the form of 72 (rows) x 36 (column) dots. More in detail, the pixels are divided into two, that is, an upper screen zone 10a of 72 x 18 dots and a lower screen zone 10b of 72 x 18 dots, as shown by a broken line in the drawing. In this connection, the division means that the upper screen zone 10a and lower screen zone 10b are driven (displayed) or non-driven (not displayed) independently of each other. More specifically, each of the pixels comprises a row electrode and a column electrode. When predetermined voltages are applied to the electrodes, the display is effected. Upon display switching, the respective electrodes are grounded so that the display is put in its non-display state. Connected to the respective electrodes are signal lines so that the controller 7 outputs a control signal to vary voltages of the electrodes to predetermined levels, thereby realizing such displaying and non-displaying operations as mentioned above. The present embodiment is arranged so that the electrodes and signal lines are divided into two groups, that is, one (upper row electrodes/signal lines 11a and upper column electrodes/signal lines 12a) for the upper screen zone 10a and the other (lower row electrodes/signal lines 11b and lower column electrodes/signal lines 12b) for the lower screen zone 10b, so that the displaying and non-displaying operations are carried out on the basis of the control signal issued from the controller 7 independently of each other for each of the upper and lower screen zones 10a and 10b. A sub-scanning position on the liquid crystal display screen 10 is detected by the controller 7 per se on the basis of a drive control signal issued from the controller 7 to the motor 8 for the sub-scanning. Thus, the controller 7, on the basis of the control signal, can judge whether the laser beam is then sub-scanning the upper screen zone 10a or sub-scanning the lower screen zone 10b, and can detect a time point at which the sub-scanning is shifted from the upper screen zone 10a to the lower screen zone 10b after completion of the sub-scanning of the upper screen zone 10a. In this way, the system can detect a sub-scanning position of the laser beam on a software basis on the basis of the control signal issued to the motor 8, which makes it unnecessary to provide such a special sensor that directly receives a YAG laser beam having a high intensity for position detection, with the result of the fact that the system can be advantageously reduced in cost. The operation of the controller 7 will be explained by referring to such a timing chart as shown in Fig. 4. Fig. 4(a) shows how upper parts A1, B1,... of the respective blocks A, B,... (refer to Fig. 5) are sequentially displayed on the upper screen zone 10a while subjected to the non-displaying operation with respect to the varying patterns, Fig. 4(b) shows how lower parts A2, B2,... of the respective blocks A, B,... (refer to Fig. 5) are sequentially displayed on the lower screen zone 10b while subjected to the non-displaying operation with respect to the varying patterns, and Fig. 4(c) shows how to main-scan the display screen at a predetermined Y position with the reflective surface 2a of the deflecting mirror or deflector 2 being fixed and how to sub-scan the display screen with the Y deflecting mirror being rotated (which rotation timing is shown by vertical lines) and with the Y position being moved. The above operation will be sequentially explained in more detail in the following. At a time point t1, when the sub-scanning of the upper screen zone 10a is completed and the marking operation of the upper part A1 of the block A is completed, which completion time point is detected by the controller 7, so that, in order to perform display switching from the block A to the next block B as shown by an arrow (1), the controller 7 controls to put the upper screen zone 10a in its non-displayed state, that is, the row and column electrodes of the pixels of the upper screen zone 10a are grounded. This enables prevention of an after-image. At a time point t2, display of the upper part B1 of the block B is activated, after which display activation time the upper part B1 of the block B is displayed on the upper screen zone 10a at a time point t3. With respect to the lower screen zone 10b, on the other hand, the lower part A2 of the block A is already activated from a time point t0 earlier than the time point t1 and thus the lower part A2 is scanned continuously from the time point t1 at which the marking of the lower part A2 is carried out. Subsequently, when the sub-scanning of the lower screen zone 10b is completed and the marking of the lower part A2 of the block A is completed at the time point t3, the controller 7 detects the then completion time point and puts the lower screen zone 10b in the non-displayed state, that is, grounds the row and column electrodes of the pixels of the lower screen zone 10b to perform display switching from the block A to the next block B as shown by an arrow (2). As a result, any after-image can be prevented. At a time point t4, display of the lower part B2 of the next block B is activated, after which display activation time the lower part B2 of the block B is displayed on the lower screen zone 10b. At the time point t3, display corresponding to one screen of block A is established and thus the marking pattern corresponding to the block A is marked on the work 13. However, display of the next block B (upper part B1) is already displayed on the upper screen zone 10a at the time point t3. This means that the marking is carried out continuously. In this way, the marking operation can be shifted to the next pattern without any intermittence and thus high-speed marking can be realized. Thereafter, in the same manner, the marking of the block B from the upper part B1 to the lower part B2 is continuously carried out at a time point t5, and then the marking from the block B to the next block C can be continuously carried out without any intermittence at a time point t6. In this way, the blocks A to L are marked without any waste time, which leads to the fact that the entire pattern 14 can be marked on the work 13 at a high speed. In the prior art, by contrast with the present invention, after the marking of the block A is done, as shown in Fig. 6, the entire display screen is put in its non-displayed state as shown by an arrow (1) so that sub-scanning is paused for a duration ▵T' before the next block B is displayed. This means that there occurs a waste time corresponding to the duration ▵T', during which no marking is carried out. In the present embodiment, it will be appreciated that, as shown in Fig. 4, since no such waste time takes place, the present embodiment can realize high-speed marking over prior art. In addition, whenever the display screen is switched (the display screen is switched between the upper and lower screen zones), the screen is put in its non-displayed state. For this reason, any after-image can also be prevented and thus the present embodiment can be suitably applied to a laser marker which uses high polymer compound type liquid crystal. As has been explained in the foregoing, in accordance with the present invention, since switching of the liquid crystal display screen is carried out between the different zones of the display screen and the zones are put in the grounded state independently of each other at the time of the switching, creation of any after-image can be prevented and high-speed marking can be attained.

Claims: A liquid crystal display for a laser marker wherein row and column electrodes are provided for each of pixels of a liquid crystal, the row (11a,11b) and column (12a,12b) electrodes are grounded and then predetermined voltages are applied to the row (11a,11b) and column (12a,12b) electrodes to perform switching of display of a liquid crystal display screen (10), a laser beam is irradiated on the liquid crystal display screen (10) and scanned on the liquid crystal display screen (10) to mark a predetermined pattern displayed on the liquid crystal display screen (10) onto a target object, the liquid crystal display comprising: display switching means for dividing the liquid crystal display screen (10) into a first zone (10a) to be firstly subjected to a sub-scanning operation and a second zone (10b) to be subjected to a sub-scanning operation following the first zone (10a), for performing switching operation of the display over the first and second zones (10a,10b) independently of each other; position detecting means for detecting a position on the liquid crystal display screen (10) at which the sub-scanning is being carried out; and means for controlling (7) the display switching means to perform switching operation of display of the first zone (10a) when the position detecting means detects completion of the sub-scanning of the first zone (10a) and to perform switching operation of display of the second zone (10b) when the position detecting means detects completion of the sub-scanning of the second zone (10b), characterized in that said display switching means is arranged for grounding the row (11a) and column (12a) electrodes for the first zone (10a) when the position detecting means detects completion of the sub-scanning of the first zone (10a) the predetermined voltages are applied to the row (11b) and column (12b) electrodes of the second zone (10b), and for grounding the row (11b) and column (12b) electrodes for the second zone (10b) when the position detecting means detects completion of the sub-scanning of the second zone (10b). The liquid crystal display for a laser marker as set forth in claim 1, wherein the sub-scanning is carried out by irradiating the laser beam and rotating a light reflector (2) for reflection of the laser beam to thereby change a reflection direction of the laser beam, and the position detecting means detects the position of the sub-scanning on the basis of a rotation command signal for the mirror (2a).

Inventors: MORI AKIRA, SAITO YOSHINORI, TSUDA YUKIHIRO, MORI, AKIRA, SAITO, YOSHINORI, TSUDA, YUKIHIRO
Applicants: KOMATSU MFG CO LTD, KABUSHIKI KAISHA KOMATSU SEISAKUSHO
Application year: 1993
Main classification: B23K26
IPC codes: G06K15, B23K26