BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a diagram schematically illustrating a typical optical disc with a markable label side;
FIG. 1B is a diagram schematically illustrating a center portion of an optical disc with a markable label side;
FIG. 2A is a schematic diagrams illustrating the cooperation of a sled and an optical ruler according to prior art;
FIG. 2B is schematic diagram illustrating the shift of the optical head on the sled in response to a control voltage according to prior art;
FIG. 2C is a schematic diagram illustrating the moving distance of a sled and the spaces of lines obtained after the marking operation of the label side of the optical disc;
FIG. 2D is a schematic diagram illustrating the lines resulting from too large moving distance of the sled;
FIG. 2E is a schematic diagram illustrating the lines resulting from too small moving distance of the sled;
FIG. 3A is a schematic diagram illustrating a saw tooth pattern of a markable optical disc provided for calibration;
FIG. 3B is a waveform diagram illustrating two square wave signals with different width generated by the optical head in response to the saw tooth pattern of FIG. 3A;
FIG. 3C is a shift vs. voltage plot varying with the width difference of the square wave signals;
FIG. 4 is a schematic diagram illustrating the relationship among the movement of a sled, the shift of an optical head carried by the sled, and a plurality of lines created by the optical head on the label side of an optical disc;
FIG. 5 is a waveform diagram schematically illustrating the calculation of the moving distance of a sled according to a tracking error signal;
FIG. 6 is a schematic diagram illustrating the calculation of the moving distance of a sled according to the address change before and after the sled moves;
FIG. 7 is a schematic diagram illustrating the calculation of the moving distance of a sled based on close loop control of the optical head; and
FIG. 8 is a schematic diagram illustrating the calculation of control voltages supplied to the optical head based on close loop control of the optical head.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Please refer to FIG. 3A and FIG. 3B, in which the relationship between the shift and the voltage realized by the optical head through the saw tooth pattern is illustrated. When the optical head focuses on the saw tooth, the photo-detector of the optical head generates a square wave signal in response to the bright and dark zones of the saw tooth pattern. As shown in FIG. 3A, on the condition that the sled is not moving, when the control voltage received by optical head is changed so as to move the optical head between the position 311 and the position 312, the width of the square waves generated by the photo-detector varies, as exemplified by the square wave signals 313 and 314 shown in FIG. 3B. According to the width time difference T1 of the square wave signal, a shift d1 of the optical head can be derived. Accordingly, as shown in FIG. 3C, a linear plot of the shift vs. control voltage of the optical head is realized. For example, if a control voltage Δv is needed for 1 μm movement of the optical head outwards along the radial direction, a control voltage −Δv will be needed to move the optical head by 1 μm inwards.
As the distance the sled moves per unit time is not always as precise as expected, the realization of the real moving distance are critical for the shift control of the optical head.
According to an embodiment of the present invention, the moving distances of a sled are tested and recorded in a memory of the optical disc recording apparatus. The recorded distances are then used in the marking operation of the label side of the optical disc together with the voltage control of the optical head for unifying the line space.
Please refer to FIG. 4, which is a scheme exemplifying the track control for the marking operation of the label side of the optical disc according to an embodiment of the present invention. In this example, the movement of the sled has been tested and a series of moving distances are recorded. For example, the first movement of the sled is 105 μm, the second movement of the sled is 98 μm, and the third movement of the sled is 95 μm.
When the moving distance of the sled is ideally 100 μm, the control voltages supplied to the optical head for marking four lines 401˜404 on the first to fourth tracks are −37.5 Δv, −12.5 Δv, 12.5 Δv and 37.5 Δv, respectively. In response, the optical head is capable of shifting to the positions 421˜424 to accomplish the even line space 25 μm. However, when the moving distance of the sled is 105 μm, which means the sled has moved 5 μm more outwards than the ideal 100 μm. Accordingly, the optical head needs to further move 5 μm inward to mark four lines 405˜408 on the fifth to eighth tracks. That is, the optical head is supplied with control voltages of −42.5 Δv, −17.5 Δv, 17.5 Δv and 32.5 Δv to shift to the positions 425˜428, thereby achieving the purpose of unifying the line space. Likewise, when the sled makes the second movement of 98 μm, which means the sled has moved 2 μm less outwards than the ideal 100 μm. Accordingly, the optical head needs to further move 2 μm outward to mark four lines 409˜412 on the ninth to twelfth tracks. That is, the optical head is supplied with control voltages of −35.5 Δv, −10.5 Δv, 14.5 Δv and 39.5 Δv to shift to the positions 429˜432, thereby achieving the purpose of unifying the line space. Moreover, when the sled makes the third movement of 95 μm, which means the sled has moved 5 μm less outwards than the ideal 100 μm. Accordingly, the optical head needs to further move 5 μm outward to mark four lines 413˜416 on the thirteenth to sixteenth tracks. That is, the optical head is supplied with control voltages of −32.5 Δv, −7.5 Δv, 17.5 Δv and 42.5 Δv to shift to the positions 433˜436, thereby achieving the purpose of unifying the line space. Subsequent tracks are processed in a similar way.
Accordingly, by testing each moving distance of the sled and recording the result in the memory of the optical disc recording apparatus, together with the voltage control of the optical head, the space of lines resulting in the marking operation of the label side of the optical disc can be unified.
The determination and recordation of moving distances of a sled can be performed before the sale of the optical disc recording apparatus. In principle, a light beam emitted by the optical head is focused on the optical disc, and the reflected light is detected by a photo-detector. The photo-detector then outputs an electric signal according to the intensity of the reflected light. The electric signal generally includes a data signal and a control signal. The data signal includes not only the data to be recorded into the optical disc but also the address information provided for position identification. The address information will be referred for determining the moving distances of the sled. The control signal includes a focusing error signal and a tracking error signal. In an embodiment, the tracking error signal is referred to for determining the moving distances of the sled.
For example, an open-loop (track-off) control mechanism of the optical head is applied. As depicted in FIG. 5, whenever the optical head under open-loop control crosses a track, the tracking error signal generates a sign wave. Therefore, by placing a common optical disc into the optical disc drive and having the data side of optical disc face the optical head, the moving distance of the sled can be obtained by multiplying the number of sign waves generated during the movement of the sled by the track pitch, e.g. 0.74 μm for DVD and 1.6 μm for CD. In this way, a series of moving distances of the sled can be determined and recorded in the memory.
Alternatively, the address information of the tracks is accessed by the optical head to calculate the moving distance of the sled. The address information is used for effectively correlating the data recorded in the optical disc to the recording positions. For example, for DVD, exclusive address information is given for every 2048 bytes of data. The address information is recorded in the identification data region (ID data region) of a data frame. The address information can be accessed from this region. For Blu-Ray Disc, every 2048 bytes of data is grouped as a data sector, and each data sector corresponds to exclusive address information. Such address information may have various types, including a physical sector number. The address information is recorded in a data frame along with common data. Therefore, after reading data from the data frame, a decoding procedure is required to extract the physical sector number, i.e. the address information of a Blu-Ray disc. In brief, for different disc specifications, different types of address information will be exhibited. The address information is recorded as different specifications and/or in different regions. Nevertheless, other address information involving correlation of the data to the recording positions can be used to calculate the moving distance of the sled. The operational principle of this embodiment will be described in more detail with reference to FIG. 6.
First of all, a common optical disc is inserted into the optical disc drive with the data side of optical disc facing the optical head. When the sled is to be moved from the position 601, the optical head at the position 602 is made in a closed-loop (track-on) control state in advance. Meanwhile, the optical head reads a first data address Addr1 of a corresponding track. Then, the optical head is switched into an open-loop (track-off) control state and the sled is moved. After the sled finishes moving, the optical head is switched into the closed-loop (track-on) control state again. Meanwhile, the optical head reads a second data address Addr2 of a corresponding track. According to the address difference between the second data address and the first data address, the moving distance of the sled can be realized. In this way, a series of moving distances of the sled can be determined and recorded in the memory.
In a further embodiment, a closed-loop (track-on) control mechanism of the optical head is applied. Please refer to FIG. 7. First of all, a common optical disc is inserted into the optical disc drive with the data side of optical disc facing the optical head. Before the sled is moved from the position 703, the optical head at the position 702 is made in a closed-loop (track-on) control state in advance. Meanwhile, the optical head locks the track 701, and then shifts to the position 702. The optical disc drive records a first control voltage required for shifting the optical head to the position 702, e.g. 30 Δv that means the optical head shifts 30 μm rightward, as shown in the figure. Then, the sled is moved while the optical head remains in the closed-loop (track-on) control state. After the sled finishes moving to the position 705 (meanwhile the optical head is at the position 704), a second control voltage supplied to the optical head is recorded, e.g. −72 Δv that means the optical head shifts 72 μm leftward, as shown in the figure. According to the difference between the first control voltage and the second control voltage, it is understood that the moving distance of the sled is 102 μm. In this way, a series of moving distances of the sled can be determined and recorded in the memory.
In addition to calculating and storing the moving distances of the sled, other embodiments of the present invention can be implemented by storing the control voltages of the optical head. Please refer to FIG. 8. First of all, a common optical disc is inserted into the optical disc drive with the data side of optical disc facing the optical head. Meanwhile, the sled is at the position 802 and the center of the sled is aligned with a certain track, e.g. track 800. After shifting the optical head by a distance of 62.5 μm to reach the position 801, the optical head is controlled in a closed-loop (track-on) control state. Meanwhile, the optical head is locking a certain track, e.g. track 820. Afterwards, the sled is moved to the position 803 while the optical head shifts to the position 804 to continue locking the track 820. The control voltage v1 required for shifting the optical head to the position 804 is recorded in the memory. Afterwards, the optical head is shifted from the position 804 to the position 805, the position 806 and the position 807 that are 25 μm, 50 μm and 75 μm from the position 804, respectively. The control voltages v2, v3 and v4 required for these shifts are also recorded into the memory. Subsequently, the optical head is shifted to the position 808 that is 25 μm from the position 807. The track, e.g. track 804, being locked by the optical head at the position 808 is recorded. The sled is then moved to the position 809 while the optical head remains locking the track 840. The control voltage v5 required for shifting the optical head to the position 810 is recorded in the memory. Afterwards, the optical head is shifted from the position 810 to the position 811, the position 812 and the position 813 that are 25 μm, 50 μm and 75 μm from the position 804, respectively. The control voltages v6, v7 and v8 required for these shifts are also recorded into the memory. Likewise, subsequent control voltages supplied to the optical head are recorded. Whenever the sled makes a movement, there will be four control voltages needed recording. After the sled finishes the movements, the control voltages of all positions of the optical head are recorded. According to these control voltages recoded in the memory, the optical head can be well controlled and moved to the desired track precisely for marking the label side of the optical disc.
According to the present invention, the movement of the sled is accurately measured in a cost-effective manner so as to improve color effect.
The present invention is intended to cover various modifications and similar arrangements included to within the spirit and scope of the appended claims, which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.
Patent Application
20070247512
