Patent Application
20080025168
Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will appreciate, electronic equipment manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not in function. In the following description and in the claims, the terms “include” and “comprise” are used in an open-ended fashion, and thus should be interpreted to mean “include, but not limited to . . . ”. Also, the term “couple” is intended to mean either an indirect or direct electrical connection. Accordingly, if one device is coupled to another device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections.
Please refer to
As shown in
According to the foregoing descriptions, it can be appreciated that the combination of the photo detector 130, the two operating units 140 and 150, the signal selector 160, and the gain stage 170 can be regarded as a sensing device for sensing the reflected light of the main beam/side beam to generate a corresponding analog signal. Hereinafter, the operations of the measuring module 110 and decision unit 120 will be described with reference to
In step 310, the measuring module 110 measures reflected light of the side beam under a first laser power P1 to generate a first value S_P1. Specifically, the decision unit 120 controls the laser diode 104 to emit light using the first laser power P1, and the photo detector 130 of the measuring module 110 detects the light reflected from the optical disc 102. In addition, the decision unit 120 controls the signal selector 160 to select the side beam sum signal SBAD corresponding to the first laser power P1 as the output signal in step 310. In this embodiment, the ADC 180 generates a plurality of first digital values corresponding to the side beam sum signal SBAD under the first laser power P1, and the calculating unit 190 averages the plurality of first digital values to generate the first value S_P1.
In step 320, the measuring module 110 measures reflected light of the main beam under the first laser power P1 to generate a second value M_P1. In this step, the decision unit 120 controls the signal selector 160 to select the main beam sum signal RFLVL corresponding to the first laser power P1 as the output signal. Accordingly, the ADC 180 generates a plurality of second digital values corresponding to the main beam sum signal RFLVL under the first laser power P1, and the calculating unit 190 then averages the plurality of second digital values to generate the second value M_P1.
In one aspect, the first value S_P1 corresponds to DC component of the reflected light of the side beam under the first laser power P1, and the second value M_P1 corresponds to DC component of the reflected light of the main beam under the first laser power P1.
In step 330, the measuring module 110 measures reflected light of the side beam under a second laser power P2 to generate a third value S_P2. In this embodiment, the decision unit 120 controls the laser diode 104 to emit light using the second laser power P2, and controls the signal selector 160 to select the side beam sum signal SBAD corresponding to the second laser power P2 as the output signal in step 330. As a result, the ADC 180 generates a plurality of third digital values corresponding to the side beam sum signal SBAD under the second laser power P2, and the calculating unit 190 averages the plurality of third digital values to generate the third value S_P2, which corresponds to DC component of the reflected light of the side beam under the second laser power P2.
In step 340, the measuring module 110 measures reflected light of the main beam under the second laser power P2 to generate a fourth value M_P2. Similar to step 320, the decision unit 120 controls the signal selector 160 to select the main beam sum signal RFLVL corresponding to the second laser power P2 as the output signal in step 340. Therefore, the ADC 180 generates a plurality of fourth digital values corresponding to the main beam sum signal RFLVL under the second laser power P2, and the calculating unit 190 averages the plurality of fourth digital values to generate the fourth value M_P2, which corresponds to DC component of the reflected light of the main beam under the second laser power P2. The relationship between amplitudes of the main beam sum signal RFLVL and the side beam sum signal SBAD with respect to different laser power levels is illustrated in
In step 350, the decision unit 120 determines a ratio α of the main beam to the side beam according to the first value S_P1, the second value M_P1, the third value S_P2, and the fourth value M_P2 generated by the calculating unit 190. In a preferred embodiment, the decision unit 120 determines the ratio α in accordance with the following formula:
α=(M—P2−M—P1)/(S—P2−S—P1) (1)
As in the foregoing illustrations, the optical storage device 100 can obtain the actual ratio of the main beam to the side beam by changing the laser power of the laser diode 104 without performing complicated mechanical operations.
Please note that separate functional blocks shown in
In the aforementioned embodiment, the measuring module 110 performs steps 310 and 320 in sequence to generate the first value S_P1 and the second value M_P1, and performs steps 330 and 340 in sequence to generate the third value S_P2 and the fourth value M_P2. This is merely an example rather than a restriction of the practical implementations. In practice, the measuring module 110 can also utilize duplicate gain stages and ADCs so as to measure reflected light of the side beam and reflected light of the main beam under a predetermined laser power in parallel. In other words, the order of the flowchart 300 is merely an example for illustrative purpose rather than a restriction of the practical implementations.
As mentioned above, once the actual ratio α of the main beam to the side beam is obtained, reliable servo control signals can be generated accordingly.
Please refer to
In a preferred embodiment, the servo control signal generator 530 comprises a first gain stage 532 and a second gain stage 534 as shown in
DRC=K
DRC*[(A+B+C+D)−α*(E+F+G+H)] (2)
where the ratio α of the main beam to the side beam is the gain of the first gain stage 532, and KDRC is the gain of the second gain stage 534. In this case, the gain KDRC is utilized for adjusting the DC level of the differential radial contrast signal DRC to a desired value.
In a preferred embodiment, the servo control signal generator 630 comprises a first gain stage 632 and a second gain stage 634 as shown in
TE=K
TE*{[(A+D)−(B+C)]−α*[(F+H)−(E+G)]} (3)
where the ratio α of the main beam to the side beam is the gain of the first gain stage 632, and KTE is the gain of the second gain stage 634. Similarly, the gain KTE is utilized for adjusting the DC level of the tracking error signal TE to a desired value.
Please refer to
FE=K
FE*{[(A+C)−(B+D)]+α*[(E+H)−(F+G)]} (4)
where the ratio α of the main beam to the side beam is the gain of the first gain stage 732, and KFE is the gain of the second gain stage 734. In this case, the gain KFE is utilized for adjusting the DC level of the focusing error signal FE to a desired value.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
