CN101599280A - Gain balance correction method for photosensitive element - Google Patents

Abstract

A gain balance correction method for a photosensitive element comprises the steps of presetting two external gain values; adjusting the projection position of the reflection light spot to deflect to one side of the photosensitive element, and respectively measuring the current output value of the photosensitive element corresponding to each external gain value; adjusting the projection position of the reflection light spot to deflect to the other side of the photosensitive element, and respectively measuring the current output value of the photosensitive element corresponding to each external gain value; calculating a gain balance value of the photosensitive element, and setting the gain balance value as an external gain value; adjusting the position of the light-sensitive element projected by the reflection light spot; and locking the projection position of the reflected light spot with the current output value of the photosensitive element equal to 0 so as to quickly finish the correction.

Description

Photosensitive element gain balance correction method

technical field

The invention relates to a method for correcting gain balance of a photosensitive element, in particular to a method for correcting gain balance of a photosensitive element receiving reflected light in a CD player.

Background technique

Optical disc drives generally use tiny light spots with a diameter of about 0.85 to 2.11 μm to be projected onto optical discs, receive reflected light from optical discs, and use electrical signals formed by differences in the amount of reflected light to servo-control the optical disc drive and read data on optical discs. Since the reflected light spot is quite small, the converted electrical signal is relatively very weak. Not only does it require gain amplification, but it also needs to ensure that the reflected light spot is projected on the receiving position in a balanced manner to improve signal quality and reliability.

As shown in FIG. 1 , it is a schematic diagram of correcting the gain balance of a photosensitive element in an existing optical disc drive. Existing optical disc drive 10 utilizes the optical system of optical pick-up head (Optical Pick-up Head) 11, the light beam that laser light-emitting diode (Laser photodiode) 12 emits is focused into a tiny spot of light (Light Spot) and projected onto Rotating disc 13. It is reflected by the optical disc 13 back to the optical pickup head 12 and projected on the optical transducer 14 to form a reflected light spot 15 . The photosensitive element 14 is divided into left and right halves of the same size, each having a gain (Gain) G1 and G2. The left and right halves of the photosensitive elements 14 are converted into current signals of corresponding magnitudes according to the luminous flux received from the reflected light point 15, and then the converted weak currents are appropriately amplified by respective gains G1 and G2 to facilitate subsequent signal processing.

When the existing optical disc drive 10 corrects the gain balance of the photosensitive element, it is performed before the Tracking Servo (Tracking Servo), and the actuator (Actuator) 16 is used to move the objective lens (Objective Lens) 17 to adjust the reflected light spot 15 projected on the photosensitive element 14. Position, so that the reflected light spot 15 is evenly projected on the left and right halves of the photosensitive element 14, so that the light receiving areas of the left and right halves are equal to eliminate the difference in receiving reflected light. Let the left and right halves of the photosensitive element 14 only have their own gain circuit differences, and use the external gain modulation device 18 to find the external gain value Kb, so that the current signals output by the left and right halves of the photosensitive element 14 after gaining each gain pass through the external gain value Kb After the gain is balanced, the output value of the subtraction operation is equal to 0, and the left and right half optical signals are balanced. When the lock track reads and writes the optical disc, the light signal difference detected by the left and right halves of the photosensitive element 14 changes, and the servo controls the optical disc drive to distinguish and read the data on the optical disc.

However, the position of the tiny reflected light spot 15 projected on the photosensitive element 14 inside the optical disk drive 10 cannot be adjusted visually, and can only be judged by the output signal. Due to the differences in the gain of the signal circuit, it is very easy for the reflected light point 15 to not fall on the center of the photosensitive element 14 after adjustment, resulting in unequal light-receiving areas of the left and right halves of the photosensitive element 14, and the difference in receiving reflected light cannot be ruled out. The magnitude of the output signal from the left and right halves of the photosensitive element 14 will include the factor of the difference in the light receiving area. Therefore, the existing method for correcting the gain balance of the photosensitive element of the optical disc player cannot calculate the external gain value Kb as the balance value from the simple gain difference, and needs to go through multiple adjustment tests to obtain it. Moreover, the obtained external gain value Kb cannot ensure that the reflected light spot 15 is in the center of the photosensitive element 14 due to the unequal difference in the light-receiving area, and cannot correctly present the difference of the light signal detected by the symmetrical left and right halves of the photosensitive element 14. Resulting in reduced signal quality and reliability. Therefore, there are still problems to be solved urgently in the gain balance correction of the existing photosensitive element.

Contents of the invention

The object of the present invention is to provide a method for correcting the gain balance of the photosensitive element, which can calculate the gain balance value of the photosensitive element to correct the gain of the photosensitive element without adjusting the reflected light spot to fall on the central position of the photosensitive element.

Another object of the present invention is to provide a method for calibrating the gain balance of the photosensitive element. According to the calculated gain balance value of the photosensitive element, the reflected light spot is quickly adjusted to the center of the photosensitive element to shorten the calibration time.

Another object of the present invention is to provide a method for correcting the gain balance of the photosensitive element to ensure that the reflected light spot is adjusted to the center of the photosensitive element, so that the subsequent operation of the optical disc drive can obtain the best signal quality and reliability.

In order to achieve the purpose of the foregoing invention, the photosensitive element gain balance correction method of the present invention first presets two external gain values; adjusts the projection position of the reflected light point to one side of the photosensitive element, and measures the current output of the photosensitive element corresponding to each external gain value value; adjust the projection position of the reflected light point to the other side of the photosensitive element, and measure the current output value of the photosensitive element relative to each external gain value; calculate the gain balance value of the photosensitive element, and set the gain balance value as the external gain value; adjust the reflection The light spot is projected on the position of the photosensitive element; the projected position of the reflected light spot where the current output value of the photosensitive element is equal to 0 is locked to quickly complete the calibration.

Among them, the calculation of the gain balance value Kc is based on two preset external gain values Kb1, Kb2, when the reflected light spot is biased to one side, the measured current output values M1, M2 and when the reflected light point is biased to the other side, the measured The current output values N1 and N2 are calculated by substituting the following equations:

$\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; Y</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; Kb</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; Kb</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; Y</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; x</span>}}$

Among them: X=M1-N1,

Y=M2-N2.

Description of drawings

FIG. 1 is a functional schematic diagram of gain balance correction of a conventional photosensitive element.

Fig. 2 is a schematic diagram of the present invention that makes the reflected light point deflect to the right.

Fig. 3 is a schematic diagram of deflecting the reflected light spot to the left according to the present invention.

FIG. 4 is a schematic diagram of adjusting the reflected light spot to a balanced position according to the present invention.

FIG. 5 is a flow chart of the method for correcting the gain balance of the photosensitive element of the present invention.

[Description of main component symbols]

10 Existing CD drives

11 Optical read head

12 laser light emitting diode

13 discs

14 photosensitive element

15 reflective dots

16 actuator

17 objective lens

18 External gain adjustment device

20 photosensitive elements

21 photosensitive element

22 External gain adjustment device

Detailed ways

In order to achieve the above object, the present invention adopts the technical means and its effects, the preferred embodiments are given, and are described as follows in conjunction with the drawings.

Please refer to FIG. 2, FIG. 3 and FIG. 4, which are the process of gain balance correction of the photosensitive element 20 of the present invention, wherein FIG. 2 shows the state where the reflected light point 21 is biased to the right, FIG. 3 is the state where the reflected light point 21 is biased to the left, and FIG. 4 is Adjust the state of the reflected light point to a balanced position. The photosensitive element 20 of the present invention is divided into left and right halves of equal size, and the left and right halves respectively have gains G1 and G2. The photosensitive element 20 is connected to an external gain modulating device 22, and the external gain modulating device 22 presets two external gain values Kb1 and Kb2. When the optical disc drive is not in the track-locking closed-back control, the present invention focuses the laser beam on the optical disc, and after being reflected by the optical disc, the reflected light spot 21 is projected on the photosensitive element 20, and then the reflected light spot 21 is deflected to the side of the photosensitive element 20 . Just like the existing optical disc drive moves the reflected light spot through the actuator, give a positive bias to control the actuator, and push the objective lens to move to one side, so that the reflected light spot 21 can be deflected to the side of the photosensitive element 20; otherwise, a negative bias can be given , then the reflected light spot 21 is biased to the other side of the photosensitive element 20; the side to which the positive and negative bias voltage makes the reflected light spot 21 deflect depends on the design of the polarity of the actuator.

As shown in FIG. 2 , in the present invention, the reflected light point 21 is first deflected to the right of the photosensitive element 20 , which is only an example but not limited to the right side first. When the present invention deflects the reflected light spot 21 to the right, the light-receiving areas of the left and right halves of the photosensitive element 20 irradiated by the reflected light spot 21 are different. For example, the entire light-receiving area of the reflected light point 21 is set as Q, the light-receiving area irradiated on the left photosensitive element 20 is set as A1, and the light-receiving area irradiated on the right photosensitive element 20 is (Q-A1). Since the magnitude of the converted current signal of the photosensitive element 20 is proportional to the light-receiving area, the conversion current ratio per unit light-receiving area is T. For the preset two external gain values Kb1 and Kb2 respectively, the equations of the current output values M1 and M2 subtracted from the left and right halves of the photosensitive element 20 are respectively:

T×A1×G1×Kb1-T(Q-A1)×G2＝M1 (1)

T×A1×G1×Kb2-T(Q-A1)×G2＝M2 (2)

Next, as shown in FIG. 3 , the present invention deflects the reflected light point 21 to the left, and the light-receiving area irradiated on the left photosensitive element 20 is set as A2, and the light-receiving area irradiated on the right photosensitive element 20 is then (Q-A2). For the preset two external gain values Kb1 and Kb2, the equations of the current output values N1 and N2 subtracted from the left and right halves of the photosensitive element 20 are respectively:

T×A2×G1×Kb1-T(Q-A2)×G2＝N1 (3)

T×A2×G1×Kb2-T(Q-A2)×G2＝N2 (4)

Subtract formula (3) from formula (1) and subtract formula (4) from formula (2) to get the current output value difference X and Y:

(A1-A2)×T×G1×Kb1+(A1-A2)T×G2=M1-N1=X (5)

(A1-A2)×T×G1×Kb2+(A1-A2)T×G2=M2-N2=Y (6)

Then divide (5) by (6) to get:

$\frac{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; Kb</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; Kb</span>}\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; x</span>}}{\mathrm{<span\; class="notranslate">\; Y</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

After formula (7) is sorted out, the proportional value of the gain G1 and G2 of the left and right halves of the photosensitive element 20 can be obtained as follows, which is defined as the gain balance value Kc:

$\frac{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; Y</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; Kb</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; Kb</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; Y</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

This gain balance value Kc can make G1*Kc=G2. That is, when the reflected light spot 21 is in the center of the photosensitive element 20, the light-receiving areas on the left and right sides are the same, and the signal after the gain of the left and right halves of the photosensitive element 20 is gained by the gain balance value Kc of the external gain modulating device 22, The output value of the subtraction is 0, reaching a state of gain balance.

Because the two external gain values Kb1 and Kb2 in the formula (8) are the known set values of the external gain modulating device 22, and the current output value difference X and Y are reflected light spot 21 deflection, relative to the external gain value The difference between the two sets of current output values M1, M2 and N1, N2 measured by Kb1 and Kb2, that is, X=M1-N1, Y=M2-N2 can be obtained or measured directly, regardless of whether the reflected light point is adjusted to The gain balance value Kc of the photosensitive element 20 can be quickly calculated due to the influence of the center of the photosensitive element or the difference of the gain circuit.

As shown in Figure 4, according to the calculated gain balance value Kc, the present invention first sets the external gain value of the external gain modulating device 22 at the gain balance value Kc, so that the output of the left and right halves of the photosensitive element 20 is subtracted The value is 0 as the target, and as shown by the arrow in the figure, the reflected light point 21 is adjusted left and right to project on the position of the photosensitive element 20 . When the locked output value is 0, it can be ensured that the reflected light point 21 falls on the center of the photosensitive element 20, so that the photosensitive element 20 can be quickly corrected to the correct gain balance.

As shown in FIG. 5 , it is a flowchart of the method for correcting the gain balance of the photosensitive element of the present invention. The present invention calculates the correct external gain value of the photosensitive element by moving the side edge of the reflected light spot, and the detailed steps of correcting the gain balance are described as follows: firstly, in step S1, the present invention starts photosensitive when the optical disc player is not in the track-locking closed-back control Component gain balance correction. In step S2, two external gain values Kb1 and Kb2 are preset to the external gain modulating device. Step S3 adjusts the projected position of the reflected light spot to deviate to one side of the photosensitive element. Step S4 measures the current output value M relative to each external gain value Kb1 and Kb2 respectively. Then enter step S5, and adjust the projected position of the reflected light spot to be biased to the other side of the photosensitive element. In step S6, the current output value N relative to each external gain value Kb1 and Kb2 is measured respectively. Next, enter step S7, and substitute the current output value relative to each external gain value Kb1 and Kb2 measured in step S4 and step S6 into the aforementioned formula (8) to calculate the specific gain balance value Kc of the photosensitive element.

Next, go to step S8 to set the external gain value of the external gain modulating device at the gain balance value Kc. In step S9, the output value of subtracting the left and right half currents of the photosensitive element is 0 as the target, and the reflected light spot is projected on the position of the photosensitive element by adjusting left and right. Go to step S10 to check whether the output value of the subtraction of the left and right halves of the current of the photosensitive element is 0? If the output value is not 0, go back to step S9 and continue to adjust the projected position of the reflected light point. If the output value is equal to 0, go to step S11 to lock the projected position of the reflected light point to ensure that the reflected light point falls on the center of the photosensitive element , and then proceed to step S12 to finish correcting the gain balance.

Therefore, the method for correcting the gain balance of the photosensitive element of the present invention can be adjusted immediately by setting Value or measurable output value, quickly and correctly calculate the specific gain balance value of the photosensitive element, and then quickly adjust and correct the reflected light point to the center of the photosensitive element according to the calculated gain balance value of the photosensitive element, so as to shorten the correction gain balance purpose of time. At the same time, the reflected light spot is correctly located in the center of the photosensitive element to ensure that when the optical disc drive is in operation, the difference in light signals detected by the two halves of the photosensitive element receiving light symmetrically can be changed, and the best signal quality and reliability can be obtained.

The above are only used to illustrate the preferred embodiments of the present invention for convenience, the scope of the present invention is not limited to these preferred embodiments, any changes made according to the present invention, without departing from the spirit of the present invention, All belong to the scope of the claims of the present invention.

Claims (6)

1. A photosensitive element gain balance correction method, which corrects the gain balance of the photosensitive element in the optical disc drive, and the steps of the correction method include: (1) Preset two external gain values; (2) Adjust the projection position of the reflected light point to one side of the photosensitive element, and measure the current output value of the photosensitive element corresponding to each external gain value; (3) Adjust the projection position of the reflected light point to the other side of the photosensitive element, and measure the current output value of the photosensitive element relative to each external gain value; (4) Calculate the gain balance value of the photosensitive element, and set the gain balance value as an external gain value; (5) Adjust the reflected light point to project on the position of the photosensitive element; (6) Locking the projection position of the reflected light spot whose current output value of the photosensitive element is equal to 0; and (7) End calibration. 2. The photosensitive element gain balance correction method according to claim 1, wherein the correction method performs correction when it is not in the closed loop control of the lock track 3. The photosensitive element gain balance correction method according to claim 1, wherein the gain balance value is represented by Kc, and is measured by two preset external gain values Kb1, Kb2, the current output value M1, M2 and The current output values N1 and N2 measured in step (3) are calculated by the following equation $\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; Y</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; Kb</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; Kb</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; Y</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; x</span>}}$ Among them: X=M1-N1, Y=M2-N2. 4. The photosensitive element gain balance correction method according to claim 1, wherein the step (2) adjusts the projected position of the reflected light point to the right of the photosensitive element, and the step (3) adjusts the projected position of the reflected light point to the left of the photosensitive element. 5. The photosensitive element gain balance correction method according to claim 4, wherein the step (5) makes the output value of subtracting the left and right half currents of the photosensitive element 0 as the target, and adjusts the reflected light point to project on the position of the photosensitive element . 6. The photosensitive element gain balance correction method according to claim 1, wherein after the step (5) adjusts the reflected light spot to project on the photosensitive element position, further comprising: Step (5-1) Check whether the current output value of the photosensitive element is 0? If it is not 0, then return to step (5), if the output value is equal to 0, then enter step (6).

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