KR100200856B1 - Driving algorithm of optical pickup - Google Patents

Abstract

An optical pickup driving algorithm is disclosed.

The disclosed driving algorithm comprises the steps of detecting a focus error signal and a track error signal; and a focus servo on step of feeding back the detected signal to an actuator for driving an objective lens to adjust a spot size formed on an optical disc. Calculating and storing the size of the primary RF signal; and adjusting the track servo on to adjust the position of the spot formed on the optical disc; and calculating and storing the size of the second RF signal; And comparing the magnitudes of the stored primary and secondary RF signals; and inverting the phase of the track error signal when the magnitude of the primary RF signal is greater than that of the secondary RF signal. (b) feeding back before the step; and performing an RF signal recording or reproducing when the magnitude of the primary RF signal is less than or equal to the magnitude of the secondary RF signal. It is a very useful invention that can be played independently of recording information such as the pit depths for playback of the recorded signal.

Description

Operation algorithm of optical pickup

(A) of FIG. 1 is a block diagram showing an optical arrangement according to an example of the optical pickup,

(b) is a schematic diagram showing an example of a four-split plate and a photoreceiving form of a photodetector.

2 is a schematic view showing one form of diffracted light received by a photodetector.

3 is a graph schematically showing a track error signal.

4 is a flowchart showing a driving algorithm of a conventional optical pickup.

5 is a flowchart illustrating a driving algorithm of an optical pickup according to the present invention.

* Explanation of symbols for main parts of the drawings

1: light source 3: light path converting means

5: objective lens 6: actuator

7 non-score lens 9 photodetector

10: optical recording medium

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a driving algorithm for optical pickup, and more particularly, to a driving algorithm for optical pickup capable of detecting a recording / reproducing signal (RF) regardless of the depth of a pit or groove.

In general, optical pickup is a device that indirectly records and reproduces information such as video and sound onto an optical recording medium, and requires good signal characteristics when recording and reproducing. For this purpose, it is essential to perform a focus servo and a track servo that detect the focus and track error signals in the beam irradiated on the optical recording medium and correct the error.

(A) and (b) of FIG. 1 are layout views showing the optical configuration of a typical optical pickup.

The optical pickup includes a light source 1 for generating and irradiating a laser beam, an objective lens 5 for forming a beam spot on the optical recording medium 10, an optical path converting means 3, and the optical recording medium ( And a photodetector 9 which receives the reflected beam at 10).

The objective lens 5 is installed in the actuator 6 in a vertical or horizontal direction with respect to the optical recording medium 10 according to a focus error signal received by the photodetector 9 and a compensation signal calculated from the track error signal. Move. The optical path converting means 3 prevents the beam irradiated from the light source 1 and incident on the optical recording medium 10 to be reflected from the recording surface of the optical recording medium 10 and to enter the light source 1 again. In general, a beam splitter is employed as the optical member employed for the purpose.

The photodetector 9 is composed of a plurality of dividers each receiving light independently. The divider is usually divided into four divisions (A, B, C, and D), and the focus error signal and the track error signal are detected by adding and subtracting the amount of light received by the four-divided divider, and the recording and reproduction signals RF (radio frequency) signal is read.

An astigmatism method is mainly used to detect the focus error signal. In this case, an astigmatism lens 7 is further provided on the front side of the photodetector, so that the objective lens 5 and the optical recording medium 1 Detect the degree of focus error according to the distance difference between As the track error signal, a push pull range is usually used. When the quadrant is divided into A, B, C, and D as shown in (b) of FIG. 1,

The focus error signal FES, the track error signal TES and the information signal RF are detected as follows.

As shown in FIG. 2, the track error signal TES detects that the amount of light due to the interference of the 0th order diffracted light and the ± 1st order diffracted light varies depending on the position of the light spot. Considering, assuming that the pit is symmetric, TES is expressed as

S ₁ : Area where the 0th diffraction light and the 1st diffraction light overlap

E ₀ : amplitude of zero diffraction light

E ₁ : amplitude of ± 1st order diffraction light

d: feet length

n: refractive index of the medium

p: track pitch

χ: The amount of light spot out of the center of the pit.

Looking at the size of TES according to the pit length, it can be seen that the sign of the TES is changed when the sine function and the pit length is d = λ / 4n as shown in FIG.

On the other hand, the general driving algorithm of the optical pickup is shown in FIG. In the first step 21, the photodetector detects the focus error signal and the track error signal by adding and subtracting as shown in equations (1) and (2). In the second step 23, the detected two error signals are fed back to the actuator driving the objective lens to perform the focus sub and track servos for adjusting the position and the spot size of the spots formed on the optical disc. In a third step 25, the detected signals are summed up as shown in equation (3) to obtain an RF (radio frequency) signal, that is, an information reproduction signal.

In detecting information with such a simple algorithm, a general optical pickup device employing a light source having a wavelength of 780 nm and a high density employing a red laser having a wavelength of 635 to 680 nm or a light source having a wavelength of 400 to 500 nm are used. It was not a problem when each of them was used exclusively for the optical pickup device.

However, maintaining compatibility with a general compact disk in a high-density empty pick-up device is a very important problem in view of the widespread use of existing compact disks.

Looking at the compatibility of the conventional compact disk and the high density compact disk with the algorithm of FIG. 4 mentioned as follows. Pit length of the existing compact disc is λ _780㎚ /4.5n - has a range of λ _780㎚ / 6n, translates it to the depth of the short wavelength light source λ _635㎚ /3.66n - bring a range of λ _635㎚ /4.88n There is a possibility that the sign of the TES signal is reversed. In other words, when playing a conventional CD using a short wavelength optical pickup has a disadvantage that the compatibility is reduced.

In addition, there is a problem in that the reproduction signal characteristics are deteriorated because the recording is performed in the center of the groove instead of the lens center during recording for the same reason as mentioned in the optical pickup for crosslink reproduction.

Accordingly, an object of the present invention is to provide an optical pickup driving algorithm that is devised in consideration of the points mentioned above and is not affected by the depth of the pit or the groove.

The driving algorithm of the empty pickup according to the present invention for achieving the above object,

Detecting a track error signal of a focus error signal; and

A focus sub-on step of feeding back the detected signal to an actuator for driving an objective lens to adjust a spot size formed on an optical disc; and

Calculating a magnitude of the first RF signal and storing the magnitude; and

A track servo on step of adjusting a position of a spot formed on the optical disk; and

Calculating a magnitude of the second RF signal and storing the magnitude; and

Comparing the calculated and stored magnitudes of the first and second RF signals; and

Inverting the phase of the track error signal and feeding back the track servo on before the size of the first RF signal is greater than that of the second RF signal; and

And performing RF signal recording or reproducing when the magnitude of the primary RF signal is less than or equal to the magnitude of the secondary RF signal.

Hereinafter, an optical pickup driving algorithm according to an embodiment of the present invention will be described in detail with reference to the accompanying FIG. 4.

The optical pickup employing the optical pickup driving algorithm of the present invention is as shown in FIG. That is, the light source 1, the objective lens 5 for forming a beam spot on the optical recording medium 10, the optical path converting means 3, and the beam reflected from the optical recording medium 10 are received. The photodetector 9 is roughly classified.

The objective lens 9 is installed in the actuator 6 in the vertical or horizontal direction with respect to the optical recording medium 10 according to the focus error signal received by the photodetector 9 and the compensation signal calculated from the track error signal. Move. The optical path converting means 3 prevents the beam irradiated from the light source 1 and incident on the optical recording medium 10 to be reflected from the recording surface of the optical recording medium 10 and to enter the light source 1 again. In general, a beam splitter is employed as the optical member employed for the purpose.

The photodetector 9 is composed of a plurality of dividers each receiving light independently. The divider is usually divided into four, and the focus error signal and the track error signal are detected by adding and subtracting the amount of light received by the four-divided divider, and the RF signal serving as the recording / reproducing signal is read out.

The driving algorithm of the optical pick-up provided as described above converts the optical signal received at each partition plate of the photodetector into an electrical signal in the first step 31, and adds and differentially amplifies the track error signal of the focus error signal. Detect.

The focus error signal detected in the second step 33 is fed back to the actuator for driving the objective lens to operate, i.e., turn on, the focus servo for adjusting the diameter of the spot formed on the recording surface of the optical disc.

In the third step 35, the RF signal (radio frequency), that is, the first RF signal, which is an information signal is calculated and stored in a state where the focus error degree is adjusted within a predetermined error range.

The track servo signal is fed back to the actuator for driving the objective lens detected in the fourth step 37 to adjust the position of the spot formed on the recording surface of the optical disc so that the optical spot travels along the correct track. Turn on

In a fifth step 39, the size of the second RF signal is calculated and stored in a state in which the track error degree is adjusted within a predetermined error range.

The sixth step 41 is a step of comparing the magnitudes of the second RF signals of the first RF signal calculated and stored. Here, when the size of the secondary RF signal is greater than or equal to the size of the primary RF signal, it indicates that a light spot is formed in the pit, and vice versa, that the light spot is formed between the pit and the pit.

The seventh step 43 may be performed by inverting the phase of the track error signal when the magnitude of the first RF signal is greater than that of the second RF signal. Give feedback before step 4. In this way, the track servo is driven by reversing the phase of the track error signal, thereby detecting the second-order RF signal in a steady state.

The eighth step 45 is to perform RF signal recording or reproducing when the magnitude of the primary RF signal is less than or equal to the magnitude of the secondary RF signal.

The optical pickup driving algorithm having such a step can detect an RF signal having good signal characteristics regardless of the pit depth of the disk or the depth of the groove. The short wavelength optical pickup provides excellent compatibility since RF signals can be detected regardless of the pit depth, that is, whether or not the phase is inverted, when reproducing information recorded on an existing optical disk.

Claims (1)

Detecting a track error signal of a focus error signal; and a focus sub-on step of feeding back the detected signal to an actuator driving an objective lens to adjust a spot size formed on an optical disc; Calculating a size and storing it; and adjusting a track servo on to adjust the position of the spot formed on the optical disc; and calculating and storing the size of the second RF signal; and calculating and storing the first RF signal. Comparing the magnitudes of the difference RF signal and the second RF signal; and inverting the phase of the track error signal when the magnitude of the first RF signal is larger than that of the second RF signal. (b) feeding back to before the step; and performing RF signal recording or reproducing when the size of the first RF signal is less than or equal to the size of the second RF signal. Driving algorithm.