CN1115689C - Device and method for automatic adjustment of optimal focus point of CD player - Google Patents

Abstract

An automatic adjusting device and method for the best focus point of an optical disk drive comprises: the RFRP circuit receives the radio frequency signal and outputs an RFRP signal; the signal processor is coupled with the RFRP circuit to measure the size of the RFRP signal; and a level shifter coupled to the signal processor for calculating the second focus bias point according to the first focus bias point and a shift bias amount, and sequentially sending the second focus bias point corresponding to the maximum RFRP signal to the signal processor, and determining whether the shift bias amount can be divided, if so, replacing the first focus bias point with the second focus bias point, and dividing the shift bias amount.

Description

Device and method for automatic adjustment of optimal focus point of CD player

The present invention relates to an optical head of an optical disc drive, and in particular to an automatic adjustment device and method for quickly searching for the best focus point of the optical disc drive by using a tree search method.

Due to the continuous improvement of information technology, the traditional disk drive (Disk) has a tendency to be gradually replaced by optical disk drive (Optical Disk Drive) due to its limited development space and small storage capacity. Due to the advantages of high capacity, etc., the optical disc drive can store a large amount of data at the same time, plus the generation of readable and writable optical discs, the optical disc drive has been widely used by the public.

However, during mass production of optical disc drives, its components, including motors, conductive elements, etc., cannot be indistinguishable, and its electronic components, such as resistors, capacitors, etc., will also change their characteristics over time. On the other hand, the ambient temperature of the user's operation will also affect the electronic components of the optical disc drive. In addition, the optical characteristics of the photo sensor (Photo Sensor) and the reflectivity of the disc itself are different, and appropriate adjustments are also required to avoid focusing errors.

Usually, in the application of the optical disc drive, the signal is generated by using the laser diode (Laser Diode) of the optical head (PickupHead) to emit laser light. This laser beam will generate a focusing point (Focusing Point) on the optical disc and then reflect back to The light sensor of the optical head part. In addition, the light sensor can be divided into two parts, one part is divided into four equal parts to generate focusing error signal (Focusing Error; FE), and the other part is divided into two equal parts to generate tracking error signal (Tracking Error; TE), these two parts will generate six current signals corresponding to the light intensity after receiving the laser respectively, and these six signals will be generated after the current-voltage converter and the pre-amplifier (Pre-Amplifier). The signals required in the application, such as focus error signal (FE), tracking error signal (TE) and radio frequency signal (RF signal), etc.

It is known from the application process of the above optical disc drive that the quality of the laser focus will directly affect the quality of the signal. In addition, the sensitivity of each part of different optical sensors is not exactly the same, so it will cause signal imbalance, which will further affect the quality of the signal. result of control.

Please refer to Figure 1, Figure 1 is a graph showing the relationship between Focus Bias and RF signal. When focusing on the best position (point a), the RF signal is at its maximum. When the reflectivity of the light sensor is different or the magnification of the preamplifier is different, it will cause the unbalance of the focusing error signal. As shown in Figure 2B. And, FIG. 2A is a graph when the focus error signal is unbalanced.

Of course, we hope that the focus position can be maintained at point a as shown in Figure 1. For example, the conventional method includes at least two methods for adjusting the focus point: one is to use manual adjustment, and this method is used in mass production, which will inevitably consume a lot of time for manual adjustment, which is very uneconomical. , will result in an increase in cost.

Another conventional method has been disclosed in Hayashi et al. US Pat. No. 5,610,886 "Automatic Focus Balance Adjustment Device and Automatic Adjustment Method".

According to this known method, if the signal (uvballance) in Figure 2B is the input of our controller, it will cause the optical head to be controlled at the wrong (error) position, such as point b in Figure 1, and at this time the error There will be an offset (Bias) between the correct position (point b) and the correct position (point a). According to this known method, first, point b is the center, and a focus offset point is defined on both sides thereof. Next, compare the RFRP signal magnitudes of the two focus offset points with the correct position (point a), and then take the focus offset point with the smallest difference between the compared RFRP signals as the center point of the next focus search. Repeat the above steps until the optical head of the CD player is controlled at the correct position (point a).

However, if at the beginning, the input signal deviates greatly from the correct position, for example, at point c, it will take a lot of time to adjust to the correct position.

Known by above-mentioned conventional method, conventional method comprises following shortcoming:

(1) When using the method of manual adjustment in mass production, it will take a lot of time for manual adjustment, which is very uneconomical and will increase the cost.

(2) According to the method of automatically adjusting the focus point of the optical disc player proposed by Hayashi et al., although it is faster than manual adjustment, when the input signal is very different from the correct position, it also needs to spend a lot of time for offsetting. Adjust the correct position.

Therefore, the object of the present invention is to provide a method for automatically adjusting the best focus point of an optical disc drive, so as to shorten the manual adjustment time during mass production.

According to another object of the present invention, a method for automatically adjusting the best focus point of an optical disc drive is provided, which uses a tree search method to achieve the purpose of fast search, and is realized in a digital manner, which has the advantages of easy adjustment and saving cost function.

According to another object of the present invention, it is to provide an automatic adjustment device for the best focus point of the optical disc player by adjusting the zero crossing point (control point) of the focus error signal so that the optical head part of the optical disc player is controlled at the best focus point. with method.

In order to achieve the above and other purposes of the present invention, the device and method for automatically adjusting the best focus point of the optical disc player provided by the present invention use a tree search method, so that the best focus point of the optical disc player can be completed in the shortest time. automatic adjustment action. Moreover, the present invention can automatically adjust the unbalanced state of the focus error signal immediately every time the system is started, so that the system can maintain the optimal condition originally designed. Moreover, the present invention is implemented in a digital manner, so it has the functions of easy adjustment and cost saving.

The present invention provides a device for automatically adjusting the best focus point of an optical disc player. The optical disc player has an optical head for reading data on an optical disc. The device for automatically adjusting the best focus point of the optical disc player includes: a The RFRP circuit is used to receive an input of a radio frequency signal, and output an RFRP signal according to the radio frequency signal, wherein the RFRP signal is a signal corresponding to a first focusing bias point; a signal processor is coupled to the RFRP circuit, Used to measure the magnitude of the RFRP signal; and a level shifter, coupled to the signal processor, used to calculate a plurality of adjacent The second focus bias point; wherein the level shifter sequentially sends out the adjacent second focus bias points, and the signal processor finds the second focus bias point corresponding to the maximum RFRP signal position, and judge whether the offset bias amount can be divided, if the offset bias amount can be further divided, replace the first focus bias with the second focus bias point corresponding to the maximum RFRP signal points, and divide the offset bias amount; and the initial position of the first focus bias point is the initial focus position of the optical disc drive.

A method for automatically adjusting the best focus point of an optical disc drive provided by the present invention includes the following steps: a. providing a first focus bias point and a first offset bias value; b. according to the first focus bias Points and the first offset bias amount are calculated to obtain a plurality of adjacent second focus bias points; c. Sequentially send out the adjacent second focus bias points, and the second focus bias points Each corresponds to a different RFRP signal, measures the magnitude of each of these RFRP signals, and finds out the position corresponding to the second focus bias point of the RFRP signal; d. judging whether the first offset bias value is It can be divided, if the first offset bias can be further divided, then replace the first focus bias point with the second focus bias point corresponding to the maximum RFRP signal, and use a second offset bias amount to replace the first offset bias amount, and repeat steps b to step d; and e. If the first offset bias amount can no longer be divided, then end the best focus point automatic adjustment action of the optical disc drive, The second focus bias point corresponding to the maximum RFRP signal is the best focus point of the optical disc drive; wherein the initial position of the first focus bias point is the initial focus position of the optical disc drive.

In order to make the above and other objects, features, and advantages of the present invention more comprehensible, a preferred embodiment is specifically cited below, together with the accompanying drawings, as follows:

Brief description of the drawings:

Figure 1 is a relationship diagram between focus offset and radio frequency signal;

Fig. 2A is a graph when the focus error signal is balanced;

Fig. 2B is a graph when the focus error signal is unbalanced;

FIG. 3 is a functional block diagram of adjusting the optical focus point of an optical disc drive according to a preferred embodiment of the present invention;

Fig. 4 is a tree search diagram of light focal points according to a preferred embodiment of the present invention; and

FIG. 5 is a flow chart of adjusting the optical focus point of an optical disc drive according to a preferred embodiment of the present invention;

Example

Please refer to FIG. 3 , which shows a functional block diagram of an optical disc player for adjusting the light focus point according to a preferred embodiment of the present invention.

The optical sensor 5 of the optical head part generates four signals A, B, C, and D after receiving the laser light reflected by the optical disc. Then, a focus error signal (FE) is generated through the amplifier 10 and a radio frequency signal (RF) is generated through the amplifier 11 . Wherein, the focus error signal is (A+C)-(B+D), and the radio frequency signal is A+B+C+D.

Next, the RFRP circuit 12 extracts the peak and bottom of the radio frequency signal (RF) into two signals, and then multiplies the two signals by a gain (Gain) and subtracts them to generate the RFRP signal.

Please refer to FIG. 3 and FIG. 4 at the same time, assuming that the focus point 19 is the initial focus position of the optical head of the optical disk drive, that is, the focus point 19 is the current focus point. First, the level biaser (Level Bias) 14 will center on the current focus point 19, and find out the offset number n and offset K that can search for the best focus point in the shortest time. Then, the level shifter 14 will sequentially generate n adjacent focus bias points according to the shift number n and the shift amount K. Assuming that n is equal to five, the distance between these five adjacent focus bias points The size (offset) is K, and each of the five adjacent focus bias points has a different RFRP signal.

Then, signal processor (Signal Processing) 13 can calculate the magnitude of each RFRP signal of these five adjacent focus bias points respectively, and find out the position of the focus bias point with the maximum RFRP signal, for example focus bias point 20 is The position of the focus bias point with the maximum RFRP signal, and then take the focus bias point 20 as the center point of the focus of the optical head, repeat the above search action until the offset cannot be divided, which means that the optical head has found the best focus point location.

On the other hand, the controller (Controller) 15 receives a focus error offset signal (FE-Offset), wherein the FE-Offset is used to adjust the center level (such as the center level Vref in FIG. 2B ) to a reference potential, The above-mentioned center level Vref is the direct current (DC) part of the focus error signal (FE).

Therefore, when there is no input of the offset (Bias), it is known from the controller's closed loop (Closed loop) theory that the controller 15 will control until the focus error signal is zero at this time, that is, the optical head will The position is controlled at the zero crossing point (Zero Crossing Point). However, when the control signal is as shown in FIG. 2B , the controller 15 will control the position of the optical head at a wrong zero-crossing point, that is, the center level Vref in FIG. 2B .

Please refer to FIG. 1 and FIG. 2B at the same time. If we want to move the position of the optical head from point b to point a, that is to say, to move our zero-crossing point from the center level Vref (solid line) in Figure 2B to the best focus position (dotted line), at this time In order to achieve the above purpose, we must add an offset to move the wrong zero-crossing point (midpoint level Vref) to our desired position (best focus position).

Therefore, the present invention provides a method for automatically adjusting the focus point of an optical disc drive, which uses a tree search method to find the best focus point. Please refer to FIG. 4 and FIG. 5 at the same time. FIG. 5 is a flowchart of a method for adjusting the optical focus point of an optical disc drive according to a preferred embodiment of the present invention.

At first, step 31: provide an initial focus bias point 19 and an offset bias K, wherein the initial focus bias point 19 is the focus position of the current optical head, and the size of the offset bias K can be Find the best focus point in the shortest time.

Step 32: Then, take the focus bias point 19 as the center point, and send n adjacent focus bias points sequentially according to the offset K, assuming that n is equal to five, at this time the five adjacent focus bias points The mutual interval size (offset) is K. Since the sent offsets are all different, the focus position will be changed, resulting in different magnitudes of RFRP signals.

Step 33: Afterwards, measure the magnitudes of the RFRP signals of the five adjacent focus points respectively, and then find out the offset that causes the maximum value of the RFRP signal, that is, use the focus bias point with the largest RFRP signal as the next time Focus point of tree search, for example focus point 20.

Step 34: Next, judge whether the offset K can be divided. If the offset K can be further divided, proceed to step 35, otherwise, end the focus adjustment work, such as step 36.

Step 35: If the offset K can be divided again, adjust the K value to a quarter of the original value at this time, that is, the offset is changed to K/4, and the focus point 20 is used as the new focus center point, and then repeat Steps 32-34, until the offset K (Bias) cannot be divided, that is, the offset K is the minimum and the RFRP signal is the maximum, which is the position of the best focus point we need.

Of course, the method of the present invention is not limited to only generating five focal points (offsets) for searching at a time, for example, two offsets, three offsets, ..., or seven offsets can be generated at one time etc. to search for the best focus point. For example, when 3 offsets are generated at a time, the distance between them is half of the previous time, and when n offsets are generated at a time, the distance between them is It is one (n-1) of the previous time. Of course, the setting of the amount of offset generated is based on the principle of finding the best focus point in the shortest time.

On the other hand, when the system is started, the system will automatically adjust the focus point regardless of whether the optical head of the optical disc player is in the best focus position, so as to avoid unbalanced signals from affecting the control results.

Therefore, the device and method for automatically adjusting the best focus point of an optical disc player provided by the present invention have the following advantages:

(1) The present invention uses a tree-like search method, which is applied to the automatic adjustment of the focus point of the optical disc drive, so it can complete the automatic adjustment of the best focus point of the optical disc drive in the shortest time, greatly improving the Knowing the disadvantages of time-consuming.

(2) The present invention can automatically adjust the unbalanced state of the focus error signal every time the system is started, so that the system can maintain the optimal condition originally designed.

(3) The present invention is realized in a digital manner, so it has the functions of easy adjustment and cost saving.

In summary, although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make various modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention is defined by the claims of the present invention.

Claims (5)

1. A device for automatically adjusting the best focus point of a CD player, the CD player has an optical head for reading data on a CD, the device for automatically adjusting the best focus point of the CD player includes: An RFRP circuit, used to receive an input of a radio frequency signal, and output an RFRP signal according to the radio frequency signal, wherein the RFRP signal is a signal corresponding to a first focus bias point, the initial position of the first focus bias point is the initial focus position of the jukebox; a signal processor, coupled to the RFRP circuit, for measuring the magnitude of the RFRP signal; and A level shifter, coupled to the signal processor, used to calculate a plurality of adjacent second focus bias points according to the first focus bias point and an offset bias amount; Wherein the level shifter sequentially sends out the adjacent second focus bias points, and the signal processor finds the position of the second focus bias point corresponding to the maximum RFRP signal, and judges the bias Whether the shift bias amount can be divided, if the shift bias amount can be divided again, replace the first focus bias point with the second focus bias point corresponding to the maximum RFRP signal, and divide the offset Bias amount. 2. The device of claim 1, wherein the device further comprises: a first amplifier, used for receiving the data read by the optical head from the optical disc, and generating a focus error signal; a second amplifier, used for receiving the data read by the optical head from the optical disc, and generating a tracking error signal; and A controller is used to control the position of the optical head at a zero-crossing point. 3. The device of claim 2, wherein the optical head further comprises: a laser diode for emitting a laser beam onto the optical disc; and A light sensor is used for receiving the reflected laser beam. 4. A method for automatically adjusting the best focus point of a CD player, comprising the following steps: a. providing a first focus bias point and a first offset bias amount, the initial position of the first focus bias point is the initial focus position of the optical disc drive; b. Calculate a plurality of adjacent second focus bias points according to the first focus bias point and the first offset bias amount; c. Sequentially send out the adjacent second focus bias points, each of which corresponds to a different RFRP signal, measure the magnitude of each of these RFRP signals, and find out the corresponding maximum value of the RFRP signal the location of the second focus bias point of the RFRP signal; d. Determine whether the first offset bias amount can be divided, and if the first offset bias amount can be divided again, replace the first focus with the second focus bias point corresponding to the maximum RFRP signal For the bias point, replace the first offset bias with a second offset bias, and repeat steps b to d; and e. If the first offset bias value can no longer be divided, then end the automatic adjustment of the best focus point of the optical disc drive, and the second focus bias point corresponding to the maximum RFRP signal is the best for the optical disc drive focus point. 5. The method according to claim 4, wherein the number of the second focus bias points is represented by n, the first bias value is represented by K1, and the second bias value is represented by K2 , then the relationship between the first offset voltage and the second offset voltage is K2=K1/(n−1).

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