JPH0477376B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method for assembling and adjusting an optical pickup used in a compact disc player, etc., and particularly to a method for quickly correcting misalignment between a split sensor and a laser beam. The present invention relates to a method for adjusting the position of a divided sensor of a suitable optical pickup.

[Background of the invention]

Compact disc (CD) players employing optical pickups are becoming popular, and the basic configuration and operation of optical pickups will be explained below with reference to FIGS. 12 to 14.

That is, after the laser beam 2 from the semiconductor laser 1 is converted into a parallel beam by the collimator lens 3,
It passes through the polarizing beam splitter 4 and passes through the 1/4 wavelength plate 5.
The quarter-wave plate 5 converts the laser light 2 from linearly polarized light to circularly polarized light. The circularly polarized laser beam 2 is focused by an objective lens 6 and irradiated onto an optical disk 7. On the other hand, the laser beam 2 irradiated onto the optical disk 7 is turned back and reflected by the optical disk 7, travels the optical path backward, and passes through the objective lens 6 again to be 1/2
The light is made incident on a four-wavelength plate 5. Here, the laser beam 2 is reversely converted from circularly polarized light to linearly polarized light, but the phase thereof is advanced by 90 degrees with respect to the original linearly polarized light. Therefore, the laser beam 2 transmitted through the quarter-wave plate 5 and incident on the polarizing beam splitter 4
(Reflected light) has its optical path bent and is guided in the direction of the detection lens 8. The laser beam 2 converged by the detection lens 8 is further subjected to astigmatism by a cylindrical lens 9 serving as an astigmatism optical system, and is then illuminated by the split sensor 10. The divided sensor 10 is usually composed of four to six light receiving elements, but FIG. 13 shows the light receiving elements 10.
An example of a divided sensor composed of parts a to 10d is shown. In addition, FIG. 14 shows the divided sensor 10
The split sensor 10 is fixed to the optical pickup main body 11 with screws 12.

By the way, if the split sensor 10 is simply assembled to the optical pickup main body 11 as shown in FIG. 14, the laser beam 2 and the light receiving elements 10a to 10d will normally be distorted due to play in the screw 12 hole or dimensional error of the split sensor 10 itself.
are not accurately aligned. Therefore, the aligned state, that is, the light receiving element 10
It is necessary to adjust the assembly position of the split sensor 10 so that the amount of light received by each of a to 10d is maximum and equal to each other. FIG. 15 shows the positional relationship between the laser beam 2 and the light receiving elements 10a to 10d in an aligned state. But to make the above adjustment(1)
(2) the split sensor 10 is located within the focal plane of the optical system composed of the detection lens 8 and the cylindrical lens 9;
Two conditions must be met: the optical disk 7 must be located within the focal plane of the objective lens 6. If condition (1) is not satisfied, the laser beam 2 causes astigmatism and becomes an ellipse as shown in FIG.
It becomes impossible to align so that the amount of light received by each of a to 10d is made equal. However, fortunately the conditions
In case (1), sufficient alignment can be ensured with the assembly precision of the optical pickup, and there is currently no practical problem. However, if condition (2) does not hold,
The laser 2 cannot be converged on the light-receiving surface of the optical sensor 10, but spreads out as shown in FIG. 17, and as a result, the amount of light received by each of the light-receiving elements 10a to 10d becomes small, making signal detection difficult. In order to satisfy condition (2), JP-A-59
In Publication No. 92443, as shown in FIG. 18, instead of the optical disk 7, a reflecting plate 13 having a translucent slit _13s and a light receiving sensor 14 are used. That is, the position of the reflection plate 13 is adjusted in the Z direction along the laser optical axis and in a plane perpendicular to the laser optical axis (XY plane) so that the amount of light received by the light receiving sensor 14 is maximized. As a result, the reflecting plate 13 can be positioned within the focal plane of the objective lens 6. However, this method requires the preparation of a special reflecting plate with slits and a mechanism for adjusting the position of the reflecting plate, which is not a preferable adjustment method in terms of cost, device scale, operability, etc.

Until now, there has been no known example of a split sensor assembly position adjustment method under conditions (1) and (2). are used as an aid to manual adjustment work. This is shown in FIG. Reference symbols 15a to 15f in the figure indicate summing amplifiers,
Reference numerals 16a to 16c represent differential amplifiers; reference numeral 17 represents differential amplifiers;
a and 17b indicate oscilloscopes, respectively. As shown in the figure, the differential amplifier 16a uses the sum signal of the amount of light received by the light receiving elements 10b and 10c to select the light receiving element 1.
A difference signal is created by subtracting the sum signal of the received light amounts of 0a and 10d, and is added to the horizontal input terminal of the oscilloscope 17a. Similarly, a difference signal obtained by subtracting the sum signal of the amount of light received by the light receiving elements 10a and 10b from the sum signal of the amounts of light received by the light receiving elements 10c and 10d is generated by the differential amplifier 16b and is applied to the vertical input terminal of the oscilloscope 17a. It's summery. Furthermore, apart from the above, a light receiving element 10
From the sum signal of the amount of light received by b and 10d, the light receiving element 10
A difference signal is generated by subtracting the sum signal of the amount of light received by the signals a and 10c, and is applied to the vertical input terminal of the oscilloscope 17b, so that its time change can be observed.

When the objective lens is excited in the laser optical axis direction at a predetermined frequency in the above configuration, a Lissage waveform indicating the direction of existence of the laser beam with respect to the light receiving elements 10a to 10d is displayed on the oscilloscope 17a.
FIG. 20 shows an example. 20th
Figure a shows the relative positional relationship between the laser beam 2 and the light receiving elements 10a to 10d, and figure b shows the corresponding Lissage waveform 19. Note that the symbol G indicates the center position of the light receiving element, and the symbol R indicates the center position of the laser beam 2.

On the other hand, each light receiving element 1 is shown in the oscilloscope 17b.
An objective lens focus error signal (hereinafter referred to as an S-curve) indicating the balance of the amount of received light from 0a to 10d is displayed, and an example thereof is shown in FIG. In this case, the symbol N indicates the point in time when the sum signal of the light receiving elements 10b, 10d becomes equal to the sum signal of the light receiving elements 10a, 10c.

However, there is a problem in that the straight line distance connecting the light receiving element center position G and the laser beam center position R cannot be specified from above the oscilloscope 17a. As shown in Figure 22 a and b, if the direction of existence of the laser beams is the same even if the straight distances are different, then
This is because the Lissage waveforms 19 are similar as shown in FIG. In addition, the light intensity of the laser beam is strongest at the center and weakens toward the periphery in a normal distribution pattern, and the laser beam receiving area of each light receiving element does not change linearly with respect to the straight line distance. This is because if the center positions G and R change relative to each other, the amount of light received by each light receiving element will change in a complicated manner. For this reason, the resurge waveform does not always show sharp directionality. on the other hand,
From the top of the oscilloscope 17b, as shown in FIG. 23a and b, even if the laser beam center positions R are different, if the center position R is on the axis of symmetry of each light receiving element, the S-shaped curve will be as shown in FIG. In other words, it becomes something similar to. Furthermore, since the objective lens is vibrated in this method, condition (2) above should be satisfied transiently twice in each vibration period, but there is a problem in that there is no means to detect when this happens. be. In other words, it is possible to know when the amount of light received by each light receiving element is balanced, but at the same time condition (2) is met.
This does not necessarily mean that it is established. Therefore, although this can be used as a guideline for maximizing and making uniform the amount of light received by each light receiving element, there remains concern about accurate determination.

Because of these performance limitations of auxiliary means, the work of adjusting the assembly position of split sensors currently relies to a large extent on repeated trial-and-error adjustments by skilled workers. Adjustments now require a lot of time.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for adjusting the position of a divided sensor in an optical pickup, which alleviates the above-described problems of the prior art and allows efficient adjustment of the position of the divided sensor assembly.

[Summary of the invention]

For this purpose, the present invention uses a scoop (SCOOP).
While the signal generation phenomenon is used to detect the focus between the optical disk and the objective lens, modeled received light amount distribution data is obtained in advance using the relative position information between the center position of the light receiving element of the split sensor and the center position of the laser beam as a parameter. By comparing and collating the received light amount data of each light receiving element obtained during adjustment (focusing), relative position information is obtained from the most approximated modeled received light amount distribution data, and based on this, The position of the divided sensor is adjusted.

[Embodiments of the invention]

The present invention will be explained below with reference to FIGS. 1 to 11.

First, the configuration for implementing the present invention will be described. FIG. 1 shows an example of the configuration. According to this, the internal structure and operation of the optical pickup main body 11 are similar to those shown in FIGS. 12 to 14, except that a monitor diode is newly added to the semiconductor laser. In this example, a semiconductor laser to which a monitor diode is added is shown separated into a semiconductor laser body 1a and a monitor diode 1b according to function, but the monitor diode 1b is a laser beam generated from the semiconductor laser body 1a. The device captures a portion of the light amount, and outputs the captured light amount as a current through photoelectric conversion. When the optical disk is positioned within the focal plane of the objective lens, the largest amount of reflected laser light travels backwards and returns to the semiconductor laser, temporarily disrupting its oscillation state and causing the monitor and Focusing between the optical disk and objective lens is detected using the so-called SCOOP signal generation phenomenon in which a pulsed current signal is generated in a diode, and this will be discussed later. .

The structure of the optical pickup main body according to the present invention is as described above, and the remaining components will be explained as follows.

(1) Storage unit 21: Modeled received light amount distribution data obtained in advance using relative position information between the light-receiving element center position G of the split sensor 10 and the laser beam center position R as parameters is stored in this storage unit 21. ing. In this case, the relative position information represents the light-receiving element center position G in X and Y coordinates when the laser beam center position R is the coordinate origin, and the light-receiving element center position G represents the assembly position of the split sensor 10. It has become a thing. FIGS. 2 to 4 show examples of the modeled received light amount distribution data as simulation results. Of these, Figure 2 shows a difference signal V _bd obtained by subtracting the amount of light received by the light receiving element 10d from the amount of light received by the light receiving element 10b.
This is a three-dimensional representation of the relationship between G and the center position G of the light receiving element. Similarly, FIG. 3 shows the light receiving element 10.
Figure 4 shows the relationship between the difference signal V _ca obtained by subtracting the amount of light received by the light receiving element 10a from the amount of light received by the light receiving element 10a and the center position _G of the light receiving element. Element center position G
This shows the relationship between This storage section 21
is designed to output the above information and data in response to requests from the central control unit 20.

(2) Vibration control unit 22...This is a functional block that controls vibration of the objective lens 6 under conditions of a predetermined frequency, constant amplitude, and variable vibration center position. The objective lens 6 is provided with a winding 22c, and when this is energized, the objective lens 6 is vibrated along the laser optical axis due to electromagnetic action with an adjacent permanent magnet (not shown). It's summery. The excitation control unit 22 is configured to energize the winding 22c to start excitation of the objective lens 6, change the center position of the vibration, or stop the excitation in response to a control command from the central control unit 20. It is something.

(3) Received light amount detection unit 23...This is a functional block that detects the amount of light received by each of the light receiving elements 10a to 10d within the divided sensor 10. Received light amount detection section 2
The specific configuration of 3 is shown in FIG. 5, and consists of four independent detection units 23a to 23d corresponding to four light receiving elements having the same circuit configuration, each of which processes the signals of the corresponding light receiving elements 10a to 10d. It's becoming like that. Numbers 35 to 40 in the figure
indicates a resistor, but to explain the signal flow here, each light receiving element 10a to 10d
From there, the amount of light received is converted into an electrical signal and output. For the sake of simplicity, only the light receiving element 10a will be described below.
The instantaneous value is held by the internal control timing. The held instantaneous value is subsequently converted into a digital signal by the A/D conversion circuit 33. The received light amount detection unit 23a outputs the digitized received light amount to the central control unit 2 via the tri-state buffer circuit 34 in response to the request from the central control unit 20.
This is output as 0.

(4) Split sensor position adjustment mechanism control unit 24...This is a functional block for adjusting and positioning the split sensor assembly position within a plane perpendicular to the irradiated laser optical axis while gripping the split sensor 10. . Based on the movement amount data and a movement start command from the central control unit 20, the divided sensor 10 is moved and positioned by the amount of movement data from the current assembly position.

(5) Semiconductor laser control section 25...This is a functional block that oscillates the laser beam 2 by supplying a constant drive current to the semiconductor laser main body 1a and controls the amount of laser light emission. Central control unit 20
The laser oscillation data from the laser oscillation data is used to control the drive current setting, start and stop of drive current supply, change of drive current value, and current increase rate at start.

(6) Monitor current detection section 26...This converts the monitor current output from the monitor diode 1b in proportion to the amount of laser light emitted from the semiconductor laser body 1a into a digital signal using a circuit configuration similar to that shown in FIG. This is a functional block. The above-mentioned detected current value is outputted to the central control section 20 in response to a request from the central control section 20.

(7) Scoop signal detection section 27...This detects and separates the pulsed scoop signal superimposed on the monitor current output from the monitor diode 1b, converts it to a TTL level, and outputs it to the central control section 20. It is a functional block.

(8) Central control unit 20...This is for comprehensively controlling each component described above, and has the following functions.

() The vibration frequency, amplitude, and vibration center position of the objective lens 6 are set and changed via the vibration control unit 22 to control the objective lens 6.

() Based on the current value obtained from the monitor current detection section 26, the start and stop of oscillation of the laser beam 2 and the amount of laser light emission are controlled via the semiconductor laser control section 25.

() Using the scoop signal obtained from the scoop signal detection section 27 as a timing reference, the amount of light received by each of the light receiving elements 10a to 10d is detected via the amount of received light detection section 23.

() Based on the amount of light received in (), the current V _{bd is} ,
Obtain each data of V _ca and V _T , and store this and storage unit 2.
Modeled received light amount data stored in 1
By comparing and verifying V _bd , V _ca , and V _T , the current coordinate position of the divided sensor is determined, and the amount of movement to reach the coordinate origin is determined.

() The divided sensor 10 is moved by the amount of movement determined in () via the divided sensor position adjustment mechanism control unit 24.
Move the assembly position.

Each component has been explained above, but its operation will be divided into four steps and shown in Figures 6 to 1.
The explanation using Figure 1 is as follows.

That is, initial settings are first performed. In this initial state, the optical pickup main body 11 is fixed to the device base, the split sensor 10 is held by the split sensor position adjustment mechanism 24 so that the assembly position can be adjusted, and the optical disk 7 is attached to the objective lens 6. It is designed to be positioned and fixed above near the focal point.

From now on, adjustments will be made in the following order of steps.

First step: While monitoring the monitor current value from the monitor current detection unit 26 under the control of the central control unit 20, the laser is driven via the semiconductor laser control unit 25 until a predetermined laser emission amount is obtained by converting the monitor current value. Increase the current _ILD gradually. This situation is shown in FIG. The start time of the step is _t0 , and control over the laser drive current _ILD is stopped at time _t1 when a predetermined amount of laser light emission is obtained.

Second step: The central control unit 20 adjusts the vibration center position of the objective lens 6 via the vibration control unit 22 until scoop signals can be stably detected at equal intervals via the scoop signal detection unit 27. do. This situation is shown in FIG. In FIG. 7, the vertical axis represents the monitor current I _M and the position of the objective lens 6 with respect to the optical disk 7 (indicated by distance L), and the horizontal axis represents time. When the objective lens 6 vibrates along a curve F with an amplitude A and an offset B, its focal point changes along a curve E, and the scoop signal S is generated only when the focal point coincides with the reflective surface H of the optical disk 7. I understand. To explain in more detail, the scoop signal S is not detected near time _t0 because the focal point E does not reach the reflecting surface H, but if the offset B is gradually increased and the vibration center position is moved toward the reflecting surface H, At the time _t1 , the curve E intersects the reflecting surface H, and therefore, the scoop signal S appears for the first time at this point of intersection. Furthermore, when reaching around time _t2 , the time intervals of the scoop signal S become equal, that is, the center position of the vibration and the reflection surface H.
The distance between them becomes equal to the focal length of the objective lens 6, thereby stabilizing the generation of the scoop signal S and completing the adjustment.

Third step: Under the control of the central control unit 20, the received light amount detection unit 2
The amount of light received by each of the light receiving elements 10a to 10d through 3
D1OUT to D4OUT are now detected. From these received light amounts D1OUT to D4OUT, the already mentioned V _bd (=D2OUT−D4OUT) and V _ca (=
D3OUT−D1OUT), V _T (= ₄ 〓 ⁱ⁼¹ D _i OUT) are calculated, and compared with V _db , V _ca , and V _T of the modeled received light amount distribution data stored in the storage unit 21. By comparing, the existence range of the light-receiving element center position G is determined. For example, in units of V
D1OUT=2.297973E−02 (=2.297973×10 ^-2 ),
D2OUT=1.640581E−02 (=1.640581×10 ^-2 ),
D3OUT=6.75527E−05 (=6.75527×10 ^-5 ),
D4OUT=1.033336E−04 (=1.033336×10 ^-4 )
In this case, the existence range K1 of the center position G of the light-receiving element determined from V _bd is determined in an arc shape as shown in FIG. 8 from the distribution data of FIG. 2 with an accuracy of ±5%. Similarly, the existence range K2 of the light-receiving element center position G determined from V _ca is determined from the distribution data of FIG. 3 as shown in FIG. 9,
Furthermore, the center position G of the photodetector obtained from V _T
The existence range K3 of
This is obtained as shown in Figure 0. Therefore, the center position G of the light receiving element can be determined as the area J where the existence ranges K1 to K3 shown in FIGS. 8 to 10 overlap. This situation is shown in FIG. Since the area surrounded by K1 to K3 is generally a triangle with arcuate sides, the coordinates of the center position G are calculated as the coordinates of the center of gravity, assuming a triangle with three intersection points connected by straight lines. It is.

Fourth step: The central control unit 20 moves the divided sensor 10 via the divided sensor position adjustment mechanism 24 in order to match the center position G of the light receiving element uniquely determined in the third step with the laser beam center position R. Position. That is, since the center position R of the laser beam is set at the coordinate origin (O, O), if the center position G of the light-receiving element is at the coordinates (x ₁ , y ₁ ), the split sensor 10 is placed on the X axis. along −x ₁ , Y
The positioning is performed by moving -y ₁ along the axis.

As described above, since the in-focus state of the objective lens and the optical disk can be detected from the scoop signal, a dedicated and large-scale mechanism and control for detecting the in-focus state is not required. Furthermore, since the relative coordinates of the light-receiving element center position G with respect to the laser beam center position R can be determined uniquely, the alignment of these center positions only needs to be performed once in principle. Furthermore, in determining the above coordinates, information regarding the X axis of the light receiving element is
V _bd = D2OUT−D4OUT, that of Y axis is V _ca =
When extracting as D3OUT−D1OUT, V _bd and V _ca are calculated by simple arithmetic operations, which saves calculation time, and V _bd and V _ca are orthogonal and well separated, as shown in Figure 11. Light receiving element center position G
Since the existing ranges K1 and K2 appear to be almost perpendicular to each other, the positioning range can be narrowed down. Furthermore, since V _T is used as information regarding the amount of laser light emission, errors in determining relative coordinates caused by variations in the amount of laser light emission with respect to the laser drive current and monitor current are reduced, and positioning accuracy is improved.

〔Effect of the invention〕

As explained above, according to the present invention, the relative positional deviation between the laser beam center position R and the light-receiving element center position G, which occurs when the split sensor is assembled to the optical pickup main body, can be adjusted by 1 to 2. This has the advantage that the sensor assembly position adjustment work can be carried out efficiently, quickly, and simply and easily by dividing the sensor assembly position adjustment work into two parts.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of one embodiment of the present invention; FIGS. 2, 3, and 4 are diagrams for explaining modeled received light amount data obtained in advance;
FIG. 5 is a diagram showing the specific configuration of the received light amount detection section in FIG. 1, FIG. 6 is a diagram for explaining the method of setting the laser drive current, and FIG. Figures 8, 9, 10, and 11 for explaining the adjustment method are as follows:
Figures 12, 13, and 14, which are diagrams for explaining the method for determining the relative coordinates of the center position of the light-receiving element with respect to the center position of the laser beam, respectively show a general optical pick-up and the configuration of this pick-up. Figures 15, 16, and 17 are diagrams showing the appearance of the split sensor and this pickup. Figures 15, 16, and 17 are diagrams for explaining the laser beam shape for the split sensor in various cases. FIG. 19 is a diagram for explaining the adjustment method for the disk reflective surface of the objective lens, and FIG. 20 is a diagram for explaining the adjustment method for the disk reflective surface of the objective lens using divided sensor output , b, Fig. 21, Fig. 22 a-c, Fig. 23 a
-c are diagrams showing the positional relationship of laser light with respect to the divided sensors and various display waveforms for explaining in more detail the adjustment method using the divided sensor outputs. 1, 1a... Semiconductor laser, 1b... Monitor
Diode, 2... Laser light, 6... Objective lens, 7... Optical disk, 8... Detection lens, 9...
...Cylindrical lens, 10...Divided sensor, 10a-1
0d... Light receiving element, 11... Optical pickup main body, 20... Central control unit, 21... Storage unit, 2
2... Vibration control section, 23... Light reception amount detection section, 24
...Divided sensor position adjustment mechanism control section, 25... Semiconductor laser control section, 26... Monitor current detection section,
27...scoop signal detection section.

Claims (1)

[Claims] 1. A method for adjusting the position of a divided sensor in an optical pickup comprising at least an objective lens with a variable position mechanism, a laser emission source with a monitor, and a divided sensor in which a plurality of light receiving elements are arranged in a predetermined manner, the method comprising: If a scoop current is detected while the objective lens is being vibrated as a variable, the received light amount data of each light receiving element at the time of detection is calculated as the relative position between the center position of the light receiving element and the center position of the laser beam. By comparing and collating the information with the modeled received light amount distribution data obtained in advance using the information as a parameter, the actual relative position information is determined from the modeled received light amount distribution data that is most similar.
A method for adjusting the position of a divided sensor in an optical pickup, which comprises adjusting the position of the divided sensor based on the information.