JP4784590B2 - Laser beam focus position deviation detection apparatus and laser beam focus position adjustment method - Google Patents

Description

  The present invention is applied to an optical head that irradiates and focuses a plurality of laser beams with the same lens, and detects a deviation between a focus position of a designated laser beam and a focus position of another laser beam. The present invention relates to a focus position deviation detection device and a laser beam focus position adjustment method for adjusting a focus position of another laser beam so that a deviation between a focus position of a designated laser beam and a focus position of another laser beam is eliminated.

  In recent years, some optical heads used when recording or reproducing data on an optical disc emit a plurality of laser beams so that the focus position on the optical disc is the same position. For example, such an optical head is an optical head that irradiates recording laser light and servo laser light, or light that irradiates information laser light and reference laser light when the optical disk is a hologram recording medium. Head, etc. In such an optical head, the focus positions of the laser beams need to be accurately adjusted.

Until now, as shown in Patent Document 1, this focus position adjustment is performed on a device called a microscope or an autocollimator through a lens in which laser light emitted from an optical head is opposed to an objective lens of the optical head. The deviation of the focus position of each laser beam is detected from the received light signal output from a light receiving element such as a CCD in the apparatus, and the focus position of the laser beam is adjusted so as to eliminate this deviation.
Japanese Patent Laid-Open No. 9-7196

  However, when it is necessary to adjust the focus positions of a plurality of laser beams with high accuracy, such as an optical head that performs recording / reproduction with respect to a hologram recording medium, a microscope or an autocollimator may shift the focus positions of the plurality of laser beams. Since the detection accuracy is insufficient, this adjustment method has a problem that the accuracy is insufficient. In addition, if an expensive microscope or autocollimator is used to increase accuracy, there is a problem that the cost required for adjusting the optical head increases.

  The present invention has been made in view of such circumstances, and a laser beam focus position shift detection device and a plurality of laser beam focus position shift detection devices capable of detecting a shift in focus position of a plurality of laser beams with high accuracy without increasing costs. An object of the present invention is to provide a laser beam focus position adjusting method capable of adjusting the laser beam focus position with high accuracy.

The focus position deviation detection apparatus for laser light according to claim 1 includes a material in which the reflectance of a portion where the laser light is focused changes when the laser light is focused by a lens and irradiated at a predetermined intensity for a predetermined time. reflectivity variable object and a table for setting the variable reflectance object, table or the optical head so that the focus position of the plurality of laser light is moved in the optical axis direction relatively at least a plurality of laser beams with variable reflectance object An adjustment signal is created by using a drive unit for driving the drive unit, a drive amount detection unit for detecting a drive amount by the drive unit, and a light reception signal output from the light receiving element of the optical head, and obtain a peak value of the adjustment signal The peak value acquisition means and the laser beam specified by the optical head are irradiated with the intensity at which the reflectivity of the spot where the laser light specified by the variable reflectivity object is focused is designated by the driving means. -Move the focus position of the laser beam in the optical axis direction of the specified laser beam, acquire the peak value of the adjustment signal by the peak value acquisition means, and reflect the spot where the laser beam specified based on the peak value is in focus Specified laser beam irradiation position adjustment means to set the location of the variable object and the laser beam specified by the optical head to the reflectivity variable object with the intensity at which the reflectivity of the location where the specified laser beam is focused changes The reflectance changing location creating means for creating the location where the reflectance has changed in the reflectance variable object, and the laser light other than that designated by the optical head is focused on the reflectance variable object by the laser light other than that designated. Irradiate with the intensity that does not change the reflectance of the spot, move the focus position of the laser beam other than specified by the drive means in the optical axis direction of the laser beam other than specified, and detect by the drive amount detection means In correspondence with the drive amount to get the peak value of the adjustment signal by peak value acquiring unit that, the laser beam focus position other than the specified focus position of the laser beam designated based optical head to a peak value obtained And a deviation detecting means for detecting the deviation.

The focus position shift detection device for laser light according to claim 2, wherein the driving means is configured such that the focus positions of the plurality of laser beams of the optical head are in the optical axis direction of the plurality of laser beams of the optical head relative to the reflectance variable object. Means for driving the table or the optical head to move in two directions perpendicular to each other and perpendicular to each other, the drive amount detection means includes means for detecting the drive amount in the two directions, and the deviation detection means comprises: The focus position of the laser beam other than that specified by the driving means is moved in two directions, respectively, and the wave of the adjustment signal is detected by the peak value acquisition means corresponding to the driving amounts in the two directions detected by the driving amount detecting means. The high value is acquired, and based on the acquired peak value, the deviation between the focus position of the specified laser beam in two directions and the focus position of the laser beam other than the specified one is detected. Characterized in that it comprises a means that.

In the laser beam focus position deviation detection device according to claim 3, when the light receiving element of the optical head is composed of the divided light receiving elements, the crest value obtaining means creates and selects a plurality of adjustment signals. It is a means for obtaining the peak value of the adjustment signal .

The focus position adjusting method of the laser beam according to claim 4 includes a material in which the reflectance of the portion where the laser beam is focused changes when the laser beam is focused by a lens and irradiated at a predetermined intensity for a predetermined time. The laser beam specified by the optical head is irradiated to the variable reflectivity object with an intensity that does not change the reflectivity of the spot where the laser beam specified for the variable reflectivity object is focused. The focus position of the laser beam specified by the drive means for driving the variable reflectivity object or the optical head to move in the optical axis direction of at least a plurality of laser beams relative to the variable object is driven in the optical axis direction of the specified laser beam. In addition, the wave height value of the adjustment signal created using the light receiving signal output from the light receiving element of the optical head is acquired, and the point where the laser beam specified based on the wave height value is focused is reflected. The specified laser beam irradiation position adjustment step to set the location where the variable rate object is set, and the intensity at which the reflectivity of the location where the specified laser beam is focused with respect to the reflectivity variable object with the laser beam specified by the optical head changes Irradiate and create a part where the reflectivity is changed on the variable reflectivity object, and create a spot where the reflectivity changes, and a laser beam other than the one specified by the optical head is combined with the laser light other than the one specified by the optical head. The amount of drive in the optical axis direction of the laser beam other than that specified by the focus position of the laser beam other than that specified by the driving means for driving the reflectivity variable object or the optical head by irradiating with the intensity at which the reflectivity of the focused spot does not change To obtain the peak value of the adjustment signal created using the received light signal output from the light receiving element of the optical head in correspondence with the detected drive amount. Based on the peak value, a deviation between the focus position of the laser beam designated by the optical head and the focus position of the laser light other than the designated one is detected, and the focus position of the laser light other than the designated one is adjusted so that the detected deviation is eliminated. And a focus position adjusting step .

According to the first and fourth aspects of the present invention, the designated laser beam is irradiated on an object containing a material whose reflectivity is changed by laser beam irradiation after being focused on the material where the reflectivity is changed. Since the focus position shift is detected from the peak value of the adjustment signal based on the reflected light when the reflectance is changed and a laser beam other than the specified one is irradiated, the focus position shift is more accurate than before. And can be adjusted so that the focus positions of a plurality of laser beams are adjusted with higher accuracy. In addition, the focus position of the laser beam other than that specified by the optical head is moved in the optical axis direction of the laser beam other than that specified relative to the variable reflectance object, and the peak value of the adjustment signal is adjusted according to the amount of movement. Since the focus position shift is detected by the peak value corresponding to the acquired movement amount, the focus position shift can be detected with higher accuracy, and the focus positions of a plurality of laser beams can be adjusted with higher accuracy. Can be adjusted.

According to the second aspect of the present invention, the focus positions of the plurality of laser beams of the optical head are added to the optical axis direction of the laser beam relative to the reflectivity variable object and are orthogonal to each other, which is the vertical direction of the optical axis direction of the laser beam. The focus position of the laser beam other than the one designated to be movable in two directions is moved in two directions, the peak value of the adjustment signal is acquired corresponding to the amount of movement, and the peak value corresponding to the acquired amount of movement is obtained. Since the focus position deviation in the two directions is detected by this, in addition to the focus position deviation in the optical axis direction of the plurality of laser beams, the focus position deviation in the two directions that are perpendicular to this direction can also be detected. Furthermore, it is possible to adjust the focus positions of a plurality of laser beams with high accuracy.

According to the invention of claim 3, since a plurality of adjustment signals are created and the peak value of the selected adjustment signal can be acquired, the adjustment signal with the highest focus position deviation detection accuracy is selected. Therefore, it is possible to detect a focus position shift with higher accuracy and to adjust the focus positions of a plurality of laser beams with higher accuracy.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of a laser beam focus position deviation detection apparatus to which the present invention is applied. 2 to 8 are flowcharts of programs executed by the controller of the laser beam focus position deviation detection apparatus. FIG. 9 is an explanatory diagram showing the movement of the laser beam and the variable reflectance object in order in detecting the focus position deviation. FIG. 10 is an explanatory diagram showing the waveform of the peak value of the reproduction signal with respect to the moving position when the phase-change optical disk, which is a variable-reflectance object, moves in the optical axis direction of the laser light with respect to the focus position of the laser light. is there. FIG. 11 is an explanatory diagram corresponding to FIG. 10 in the case where the entire reflectance variable object is a material whose reflectance changes. FIG. 12 shows the waveform of the peak value of the reproduction signal with respect to the movement position when the reflectance variable object is moved with respect to the focus position of the laser light after the reflectance of the reflectance variable object is changed by laser light irradiation. It is explanatory drawing shown. FIG. 13 shows a focus error signal and an X-direction error signal for the moving position when the reflectivity variable object is moved with respect to the focus position of the laser light after changing the reflectivity of the reflectivity variable object by laser light irradiation. FIG. 6 is an explanatory diagram showing a waveform of a peak value of a Y direction error signal.

  The stage 10 of the laser beam focus position deviation detection device 1 shown in FIG. 1 has a flat plate surface, and a rectangular parallelepiped upright member 12 is provided at one location. A predetermined shape of the rectangular parallelepiped upright member 12 is provided. Two mounting rods 14 for setting the optical head 18 are provided at the locations. The two mounting rods 14 hold the optical head 18 by being inserted into holes of the optical head 18. Further, the stage 10 has a step of a hole in which a laser beam irradiated from the optical head 18 sets a reflectance variable object M of the table 20 described later when the optical head 18 is set by an inclination adjusting mechanism (not shown). It is adjusted to be perpendicular to the plane and the surface of the variable reflectivity object M.

  The table 20 has a hole with a step for setting the variable reflectance object M on a flat plate. As the reflectivity variable object M, any thin plate-like material including a material whose reflectivity changes when laser light irradiation is performed for a predetermined time can be used. The reflectivity variable object M may be entirely made of a material whose reflectivity changes by laser light irradiation. What can be most easily prepared is a phase change type optical disc in which an uninitialized phase change film is used as a recording layer.

  The table 20 is attached to a moving body 22, and the moving body 22 is movable by a frame body 26 only in the height direction (hereinafter referred to as Z direction). A shaft connected to the motor 24 passes through the screw hole of the moving body 22, and the moving body 22 moves in the Z direction by the rotation of the motor 24. The motor 24 is driven by a Z-direction moving motor control circuit 200 described later. The motor 24 has an encoder 24a, which outputs two pulse signals φA and φB having a high level and a low level at every predetermined rotation angle. The two pulse signals φA and φB are shifted in phase by π / 2, and the signal whose phase is advanced changes depending on the rotation direction. Therefore, the direction of movement can be determined by detecting which pulse signal is advanced in phase. It has come to understand.

  The frame body 26 and the motor 24 are attached to and fixed to the moving body 28. The moving body 28 can be moved only in the horizontal direction (hereinafter referred to as the X direction) by the frame body 34. A shaft 30 connected to the motor 32 passes through the screw hole of the moving body 28, and the moving body 28 moves in the X direction by the rotation of the motor 32. The motor 32 is driven by an X-direction moving motor control circuit 210 described later. The motor 32 has an encoder 32a, which outputs two pulse signals φA and φB having a high level and a low level for each predetermined rotation angle. The two pulse signals φA and φB are shifted in phase by π / 2, and the signal whose phase is advanced changes depending on the rotation direction. Therefore, the direction of movement can be determined by detecting which pulse signal is advanced in phase. It has come to understand.

  The frame 34 can be moved only in the direction perpendicular to the paper surface of FIG. 1 (hereinafter referred to as the Y direction) by the base 36. A shaft (not shown) connected to the motor 38 passes through the screw hole of the frame body 34, and the frame body 34 moves in the Y direction by the rotation of the motor 38. The motor 38 is driven by a Y-direction moving motor control circuit 220 described later. The motor 38 has an encoder 38a, which outputs two pulse signals φA and φB having a high level and a low level for each predetermined rotation angle. The two pulse signals φA and φB are shifted in phase by π / 2, and the signal whose phase is advanced changes depending on the rotation direction. Therefore, the direction of movement can be determined by detecting which pulse signal is advanced in phase. It has come to understand.

  The moving bodies 22, 28 and the frame 34 are moved in the Z direction, the X direction, and the Y direction, respectively, by driving the motor 24, the motor 32, and the motor 38, whereby the table 20 and the reflectivity variable object M are moved in the Z direction, X Move in the direction, Y direction.

  The Z-direction movement motor control circuit 200 drives the motor 24 in a certain direction when the drive limit position movement command is input from the controller 300, and stops driving when a signal is input from the Z-direction position detection circuit 202 described later. To do. When the movement position is input from the controller 300, the motor 24 is driven until the movement position input from the Z-direction position detection circuit 202 described later becomes equal to the movement position input from the controller 300. The Z-direction position detection circuit 202 outputs a signal indicating the drive limit position to the Z-direction movement motor control circuit 200 when the pulse signal input from the encoder 24a stops after the drive limit position movement command is input from the controller 300. The count value of the number of pulses of the pulse signal is set to zero. Then, the drive limit position is set to position 0, the number of pulses of the pulse signal input thereafter is counted, and the movement amount is calculated and output as the Z-direction position. At that time, the direction of movement is detected from the phase difference between the two pulse signals. If the direction of movement is away from the drive limit position, the count value is added to the count value so far, and the direction toward the drive limit position is reached. If it is, the count value is subtracted from the previous count value.

  The X-direction movement motor control circuit 210, the X-direction position detection circuit 212, the Y-direction movement motor control circuit 220, and the Y-direction position detection circuit 222 are the same as the Z-direction movement motor control circuit 200 and the Z-direction position detection circuit 202 described above. Perform the operation.

  When a laser irradiation start command is input from the controller 300, the laser driving circuit A120 outputs, to the laser light source of the optical head 18, a voltage and current at which the laser light having the laser light intensity input from the controller 300 is emitted at the same time. Similarly to the laser drive circuit A120, when the laser irradiation start command is input from the controller 300, the laser drive circuit B122 also outputs the voltage and current of the intensity at which the laser beam with the laser beam intensity input from the controller 300 is emitted from the optical head 18. Output to laser light source.

The signal amplification circuit 100 amplifies and outputs a signal input from the light receiving element of the optical head 18. The reproduction signal generation circuit 102, the focus error signal generation circuit 104, the X direction error signal generation circuit 106, and the Y direction error signal generation circuit 108 perform the following calculation if the light receiving element of the optical head 18 is a four-divided light receiving element. Output the signal. A, B, C, and D are obtained from the light receiving element at the upper right of the four-divided light receiving element when the light spot formed on the light receiving element is viewed in the Y direction corresponding to the light spot formed on the reflectivity variable object M. A, B, C, D are shown around the clock.
Reproduction signal generation circuit 102: A + B + C + D
Focus error signal generation circuit 104: (A + C)-(B + D)
X direction error signal generation circuit 106: (A + B)-(C + D)
Y direction error signal generation circuit 108: (A + D)-(B + C)
The reproduction signal generation circuit 102 is a circuit that calculates and outputs the sum of the input signals. If the light receiving element of the optical head 18 is not divided into four parts, the sum of the divided signals is calculated and output. . The other circuit outputs a signal obtained by performing the same calculation as described above even if the light receiving element of the optical head 18 is not divided into four. As will be described later, in such a case, these signals are not used as adjustment signals.

  The signal switching circuit 110 outputs a signal designated by the controller 300 among the four input signals to the A / D converter 112 described later. The A / D converter 112, when a peak value acquisition command is input from the controller 300, samples the peak value of the input signal into digital data, and outputs the digital data to the controller 300.

  The controller 300 starts a program stored in the memory in response to a command from the input device 304 such as a keyboard or a mouse, issues a command to each circuit, and uses digital data input from the A / D converter 112. The focus position deviation of the laser beam is calculated, and the calculation result is output to the display device 302 which is a display composed of CRT, liquid crystal and the like.

  When adjusting the focus position of the laser beam of the optical head 18 using the laser beam focus position deviation detection apparatus 1 configured as described above, the operator holds the optical head 18 on the mounting rod above the stage 10. 14, the optical head 18 is set, and the reflectivity variable object M is set in the hole of the table 20. The following description will be given on the assumption that the reflectivity variable object M is a phase-change optical disc in which an uninitialized phase-change film that can be prepared most simply is a recording layer.

  In this case, the designated laser beam is the laser A driven by the laser drive circuit A120, and the focus position of the laser beam B driven by another laser drive circuit B122 is adjusted to the focus position of the laser beam A. And In the optical head 18 to be adjusted, the optical axis of the objective lens and the optical axis of the laser light are adjusted by an autocollimator and a Shack-Hartmann sensor or an interferometer.

  Next, the operator inputs an initial position in the X direction and initial positions Xf and Yf in the Y direction from the input device 304. This position is a position in the X direction and the Y direction at which the laser beam having the intensity with variable reflectivity is irradiated onto the reflectivity variable object M. If the reflectivity variable object M has not been used so far, an arbitrary position where the laser beam is irradiated to the reflectivity variable object M may be set as the initial position. The initial positions Xf and Yf are input so as to avoid. If the input initial positions Xf and Yf are stored in the controller 300 in correspondence with the number of the reflectance variable object M, the reflectance variable object M remains set in the hole of the table 20 or is set. If the position is fixed, the initial positions Xf and Yf stored in the controller 300 can be displayed on the display device 302, and the initial positions Xf and Yf of this time can be input.

  Next, the operator inputs the start of the program of the flow shown in FIGS. 9A. As shown in FIG. 9A, this program implements the focus position of the laser beam A to the position of the recording layer of the phase change optical disc that is the reflectivity variable object M by moving the table 20, and FIG. As shown in FIG. 9B, the recording layer is phase-changed with the laser beam A (the reflectance is changed), and the laser beam is moved by moving the table 20 in the Z direction, the X direction, and the Y direction as shown in FIG. The focus position of B is moved, the peak values at the respective positions are acquired, and the deviation of the focus position of the laser light B from the focus position of the laser light A is calculated from the acquired peak values at the respective positions.

  Hereinafter, it demonstrates along the flowchart of FIGS. In the following description of the present embodiment, the reference numerals in parentheses correspond to the reference numerals in FIGS.

First, the program starts (S100), and a counter and the like are initialized (S102). Then, since an instruction is displayed on the display device 302 to select a signal to be used for adjustment, the operator selects an adjustment signal to be used for adjustment in the X, Y, and Z directions from the input device 304 from the following (S104). .
X direction: reproduction signal, X direction error signal Y direction: reproduction signal, Y direction error signal Z direction: reproduction signal, focus error signal The reproduction signal is an output signal of the reproduction signal generation circuit 102, and the focus error signal is a focus error signal. The output signal of the generation circuit 104, the X direction error signal is an output signal of the X direction error signal generation circuit 106, and the Y direction error signal is an output signal of the Y direction error signal generation circuit 108. At this time, if the light receiving elements of the optical head 18 are not the four-divided light receiving elements, all reproduction signals are selected. Even in the case of a four-divided light receiving element, the reproduction signal is selected even when the focus error, tracking direction error, and circumferential direction error are not calculated by the above-described equations.

  Next, commands are sent to the Z-direction movement motor control circuit 200, the Z-direction position detection circuit 202, the X-direction movement motor control circuit 210, the X-direction position detection circuit 212, the Y-direction movement motor control circuit 220, and the Y-direction position detection circuit 222. The motors 24, 32, 38 move to the drive limit position, and the position at this time is set to 0 (S106). Then, the initial positions Xf and Yf previously input and stored by the operator are output to the X direction movement motor control circuit 210 and the Y direction movement motor control circuit 220, and the X direction position and the Y direction position are the initial positions Xf, It becomes Yf (S108).

  Next, the Z-direction initial position Zf is set, and the Z-direction position is set to the initial position Zf (S110 to S150). As shown in FIG. 9A, the phase change type optical disk that is the variable reflectivity object M has a structure in which a recording layer and a reflective layer are provided under a transparent substrate, and the initial position Zf in the Z direction is This is the position where the focus position of the laser beam A is aligned with the recording layer. Specifically, first, the output signal of the signal switching circuit 110 is used as a reproduction signal (S110), and irradiation of the laser light A is started with an intensity that does not cause a change in the recording layer of the phase change optical disk that is the reflectivity variable object M. (S112).

  Subsequently, the peak value of the reproduction signal is captured (S114), and it is detected that the focus position of the laser beam A has become a position near the recording layer of the phase change optical disk due to the change in the peak value of the reproduction signal. While performing processing to capture the peak value necessary for calculating the initial position Zf (S116 to S134), the focus position of the laser beam A approaches the phase change optical disc that is the reflectivity variable object M at intervals of Az. It moves (S136, S138). As shown in FIG. 9A, the peak value of the reproduction signal becomes high when the focus position matches the surface and the recording layer. A curve of the peak value of the reproduction signal with respect to the position in the Z direction is drawn as shown in FIG.

  The peak value of the reproduction signal is taken in, and it is detected that the focus position of the laser beam A has become a position near the recording layer of the phase change optical disk due to the change in the peak value of the reproduction signal, and the initial position Zf is calculated from that position. In the processing (S114 to S134) for acquiring the peak value necessary for the measurement, SL is set to 1 when the acquired peak value exceeds the predetermined level H (S118, S120), and the next acquired peak value is smaller than the predetermined level H. When SL is reached, SL is set to 2 (S124, S126), and m is incremented by 1 from the time when the acquired peak value exceeds the predetermined level H until the acquired peak value becomes equal to or lower than the predetermined level H ( S130) The peak values I (0) to I (m) are stored (S114). The locations where dots are shown in FIG. 10 are locations where the peak values I (0) to I (m) are stored. When the Z-direction moving distance exceeds the set limit distance (S140-YES), there is a cause such as placing an incorrect sample, so the irradiation of the laser beam A is stopped (S142), and the display device 302 is displayed. Abnormality is displayed (S144), and the program is terminated (S146).

When SL becomes 3 (S132) and the crest value falls below the predetermined level H (S128-NO, S134-YES), the crest values I (0) to I (m) and the Z direction position are as follows: It corresponds to.
I (m), I (m-1), I (m-2) ... I (0)
n.Az, (n-1) .Az, (n-2) .Az ..... (nm) .Az
From this, a curve of the peak value with respect to the Z direction position is created by the method of least squares, and the Z direction position of the local maximum point (the place where the value of the expression obtained by differentiating the equation of the curve becomes 0) is calculated. (S148). Then, it moves to the calculated initial position Zf in the Z direction (S150). Next, the laser beam A is irradiated for a predetermined time at an intensity at which a phase change occurs in the recording layer of the phase change optical disc (the reflectance changes) (S152 to S158). Then, the data of the crest values I (0) to I (m) that have become unnecessary are cleared (S160).

  Next, a deviation DevZ in the focus position in the Z direction is detected (S162 to S220). Specifically, the counter or the like is cleared (S162), and the laser beam B is irradiated with an intensity at which no change occurs in the recording layer of the phase change optical disk (S164). It is determined whether the peak value to be captured is a reproduction signal (S168-YES) or a focus error signal (S168-NO), and processing is performed in the case of a reproduction signal (S170 to S184) and in the case of a focus error signal (S188 to S210). I do.

  In the case of a reproduction signal, the signal is moved at intervals of Bz from the initial position Zf (S176), the peak value is taken in at each moving position (S170), and when the peak value becomes smaller than the predetermined level RH (S172-YES), This time, it moves in the reverse direction at an interval of Bz from the initial position Zf (S178), and the crest value is captured at each moving position until the crest value becomes smaller than the predetermined level RH (S182-YES) (S180). When visually shown, the peak value at the location indicated by the dot is stored as shown in FIG.

  Further, in the case of a focus error signal, it moves at intervals of Bz from the initial position Zf (S200), takes a peak value at each moving position (S190), and the peak value becomes smaller than a predetermined level FH (S194-YES). ) And the difference from the previous peak value is smaller than the predetermined difference FDe (S196-YES), this time, it moves in the reverse direction at an interval of Bz from the initial position Zf (S202), and the peak value is predetermined. The peak value is stored at each moving position until it becomes smaller than the level FH (S207-YES) and the difference from the previous peak value becomes smaller than the predetermined difference FDe (S208-YES) (S204). Visually, the crest value at a location indicated by dots as shown in FIG. 13 is stored.

Note that the movement interval Bz is set to be smaller than the movement interval Az in the process for detecting the Z-direction initial position Zf first in order to increase the detection accuracy of the focus position deviation. After confirming that the value (n + m) representing the movement distance is a predetermined value or more in the case of the reproduction signal and the focus error signal (S185, S212), the Z-direction deviation DevZ is calculated (S218). . At this time, the peak values I (0) to I (n + m) correspond to the Z-direction position as follows.
I (0), I (1), I (2)... I (n), I (n + 1), I (n + 2).
Zf, Zf + Bz, Zf + 2Bz..Zf + n.Bz, Zf-Bz, Zf-2Bz..Zf-mBz

  In the case of a reproduction signal, a curve of the peak value with respect to the Z direction position is created by the least square method, and the Z direction position of the local maximum point (the place where the value of the expression obtained by differentiating the curve expression is 0) is calculated. Deviation DevZ from the initial position Zf in the direction is calculated. In the case of a focus error signal, a peak value curve with respect to the Z direction position is created by the least square method to calculate the Z direction position where the curve crosses zero, and the deviation DevZ from the initial position Zf in the Z direction is calculated. To do.

  The calculated DevZ value and the waveform curve of the peak value are displayed on the display device 302 (S219), and the peak value data that is no longer needed is cleared (S220). When the value (n + m) representing the moving distance is equal to or smaller than a predetermined value, that is, the focus position deviation in the Z direction is large, and the peak value of the reproduction signal is smaller than the predetermined level RH from the beginning, or the peak value of the focus error signal is predetermined. If the difference from the level FH and the previous peak value is smaller than the predetermined difference FDe, predetermined processing is performed (S222 to S244). This process moves from the initial position Zf at intervals of Az (S222), searches for a point where the peak value of the reproduction signal is greater than a predetermined level SH (S224, S226), and sets that position as Zc (S228). This is a process for returning to the process (S230). In this case, if a location where the peak value of the reproduction signal is greater than the predetermined level SH in both directions from the initial position Zf is not found (S232-YES, S234-YES), the focus position deviation is too large in the X and Y directions and cannot be detected. Therefore, an abnormality is displayed (S144) and the program is terminated (S146).

  Next, when the detection of the focus position deviation in the Z direction is completed, the focus position deviation in the X direction is detected (S246 to S298). In this case, after the position in the Z direction is set to Zf + DevZ (S246), the only difference is that the movement direction is the X direction and that the adjustment signal is an X direction error signal when the adjustment signal is not a reproduction signal. The processing for detecting misalignment and the processing method are the same. In this case, since the Z direction position is set to the most appropriate position of Zf + DevZ, the peak value of the reproduction signal is initially smaller than the predetermined level RH, or the peak value of the X direction error signal is smaller than the predetermined level TH and 1 Since the difference from the previous peak value is not smaller than the predetermined difference TDe, this corresponds to the process of searching for a position where the peak value of the reproduction signal is higher than the predetermined level SH and setting the position to Zc (S222 to S244). There is no processing to do.

  When the detection of the focus position shift in the X direction is finished, the calculated value of the focus position shift DevX in the X direction and the waveform curve of the peak value are displayed on the display device 302 (S296), and the unnecessary peak value data is cleared. (S298), the focus position shift in the Y direction is detected (S300 to S352). In this case, after the position in the X direction is set to Xf + DevX (S300), only the point that the moving direction is the Y direction and the point that the Y direction error signal is different when the adjustment signal is not a reproduction signal is different. The processing for detecting misalignment and the processing method are the same. In this case as well, as in the process of detecting the focus position deviation in the X direction, a process corresponding to the process (S222 to S244) for searching for a location where the peak value of the reproduction signal is greater than the predetermined level SH and setting the position to Zc is performed. Absent.

  Next, the calculated value of the focus position deviation DevX in the X direction and the waveform curve of the crest value are displayed on the display device 302 (S352), and the crest value data that is no longer needed is cleared (S354). "Adjustment continued?" Is displayed (S356). The operator views the focus position shift in the X, Y, and Z directions displayed on the display device 302, inputs No if it is determined that it is within the allowable limit, and Yes if it determines that adjustment is necessary. input. If No (S358-NO), the program ends (S364). If Yes (S358-YES), the display device 302 displays "Adjustment complete?" (S360) and waits for the operator to enter Yes (S362).

  The operator moves the focus position in a direction in which the detected deviation disappears by adjusting the position of the component in the optical head 18. The position of the focus position in the Z direction is mainly adjusted by moving the collimating lens in the optical axis direction of the laser beam, and the position of the focus position in the X and Y directions is mainly adjusted by adjusting the position and inclination of the laser light source. adjust. When it is desired to detect the focus position shift again, “Yes” is input (S362—YES). As a result, the program returns to the process of detecting the focus position deviation DevZ in the Z direction (S162), and the focus position deviation in the X, Y, and Z directions is detected by the same process as described above. By repeating this process, the focus position deviation falls within the allowable limit, and when “Continue Adjustment?” Is displayed on the display device 304 (S356), No is input (S358—NO), and the program ends. (S364). If it is determined that adjustment cannot be performed while the optical head 18 is fixed on the stage 10, Yes is input even if the adjustment is not completed (S358-YES), the program is terminated (S364), and the optical head 18 is moved. After the adjustment, it is set on the stage 10 again, and the program processing for detecting the focus position deviation is performed from the beginning.

As described above, according to the laser beam focus position deviation detection device 1 of the present embodiment, the laser beam to be specified is reflected with respect to an object (reflectance variable object M) containing a material whose reflectivity is changed by laser light irradiation. Focus position on the material where the rate changes and then irradiate to change the reflectivity, and detect the focus position deviation from the peak value of the adjustment signal based on the reflected light when irradiated with laser light other than specified Therefore, it is possible to detect a focus position shift with higher accuracy than before, and to adjust the focus positions of a plurality of laser beams with higher accuracy.

Further, the focus position of the laser beam of the optical head 18 is moved relative to the reflectance variable object M in the optical axis direction of the laser beam, the peak value of the adjustment signal at each moving position is acquired, and the acquired moving position By detecting the focus position deviation based on the crest value at, the focus position deviation can be detected with higher accuracy from the moving position and crest value, and adjustment is performed so that the focus positions of a plurality of laser beams can be adjusted with higher accuracy. be able to.

Further, the focus position of the laser beam of the optical head 18 can be moved in two directions perpendicular to the optical axis direction of the laser beam in addition to the optical axis direction of the laser beam relative to the reflectivity variable object M. By doing so, in addition to the focus position shift in the optical axis direction of the laser light, a focus position shift in two directions that are perpendicular to this direction can also be detected, so that the focus positions of a plurality of laser beams can be adjusted with higher accuracy. Can be adjusted.

In addition, by creating multiple adjustment signals and acquiring the peak value of the selected adjustment signal, it is possible to select the adjustment signal with the highest focus position deviation detection accuracy, so focus can be achieved with higher accuracy. A positional shift can be detected, and adjustment can be performed so that the focus positions of a plurality of laser beams are adjusted with higher accuracy.

  Various modifications can be made to the above embodiment. In the above embodiment, the focus position of the laser beam of the optical head 18 is moved relative to the reflectivity variable object M by moving the table 20, but instead of moving the table 20, the stage 10 may be moved. Alternatively, the rectangular parallelepiped upright member 12 to which the mounting rod 14 for setting the optical head 18 is attached may be moved. In the Z direction, a focus actuator that drives the objective lens of the optical head 18 may be driven to move the objective lens in the Z direction. Also by this, the same effect as the above embodiment can be expected.

  In the above embodiment, the phase change type optical disc that is not initialized is used as the reflectivity variable object M. However, any optical disc can be used as long as the reflectivity is changed by laser light irradiation. For example, the reflectance variable object M may be a flat plate made of the same material as that of the recording layer of the phase change optical disk. In this case, the initial position Zf in the Z direction is obtained by attaching a high reflectivity sheet on the surface of the variable reflectivity object M opposite to the optical head 18 side, and reproducing signals from the position of the first maximum position as shown in FIG. What is necessary is just to set to the position of Th2 which is a half of the width | variety Thl between two local maxima in the peak value curve. Further, if the thickness of the reflectivity variable object M is known, the position may be set to a position of (thickness / 2) from the position of the first local maximum. Also by this, the same effect as the above embodiment can be expected.

  Further, in the above embodiment, the peak value of the reproduction signal is used to set the initial position Zf in the Z direction. However, if the expression of the focus error signal of the optical head 18 is (A + C) − (B + D) described above. The peak value of the focus error signal may be used. In this case, a point where the waveform of the peak value with respect to the position crosses zero may be set as the initial position Zf. By this, the same effect as the above embodiment can be expected.

  Further, in the above-described embodiment, the focus position shift in the X, Y, and Z directions is detected. However, the optical axis of the objective lens and the light of the laser beam are adjusted before the adjustment according to the present invention in the X and Y directions. If only the adjustment for aligning the axis is sufficient, only the focus position shift in the Z direction may be detected and only the focus position adjustment in the Z direction may be performed. According to this, since the configuration of the apparatus becomes simple, the cost can be suppressed.

  Furthermore, in the above embodiment, the table 20 and the reflectance variable object M are moved relative to the focus position of the laser beam to obtain a waveform curve of the peak value with respect to the position, and the focus position shift is detected. The table 20 and the reflectivity variable object M are kept fixed, the wave height value when the focus position is matched is obtained in advance, and the focus position deviation is determined by the ratio of the acquired wave height value to the wave height value when the focus position is matched. You may make it detect. According to this, although the detection accuracy of the focus position shift is poor, the focus position only needs to be adjusted until the acquired peak value becomes the peak value when the focus position is matched, so the focus position adjustment accuracy does not deteriorate so much. . In addition, since the configuration of the apparatus is simplified, the cost can be suppressed.

  Furthermore, in the above embodiment, the signal for detecting the focus position shift is selected, but the signal may be only the reproduction signal and may not be selected. According to this, since the configuration of the apparatus becomes simple, the cost can be suppressed.

  Furthermore, in the above embodiment, the peak value of the signal is acquired as digital data by the A / D converter 112 and stored in the controller 300. However, the peak value of the signal is detected visually by inputting the signal to an oscilloscope or the like. Alternatively, the detected peak value may be processed by computer processing or manual calculation to calculate the focus position deviation. This also simplifies the configuration of the apparatus, thereby reducing the cost. As described above, various modifications can be made without departing from the object of the present invention.

  As described above, according to the present invention, it is possible to provide a focus position deviation detection device and a laser beam focus position adjustment method capable of detecting a deviation of a focus position of a plurality of laser beams with high accuracy without increasing costs. can do.

It is a block diagram which shows the whole structure of the focus position shift detection apparatus of the laser beam to which this invention was applied. It is a flowchart of the program which the controller of the focus position shift detection apparatus of the laser beam performs. It is a flowchart of the program which the controller of the focus position shift detection apparatus of the laser beam performs. It is a flowchart of the program which the controller of the focus position shift detection apparatus of the laser beam performs. It is a flowchart of the program which the controller of the focus position shift detection apparatus of the laser beam performs. It is a flowchart of the program which the controller of the focus position shift detection apparatus of the laser beam performs. It is a flowchart of the program which the controller of the focus position shift detection apparatus of the laser beam performs. It is a flowchart of the program which the controller of the focus position shift detection apparatus of the laser beam performs. It is explanatory drawing which showed in order the movement of the laser beam and reflectance variable object in focus position shift detection. FIG. 5 is an explanatory diagram showing a waveform of a peak value of a reproduction signal with respect to a moving position when a phase change optical disc, which is a variable-reflectance object, moves in the optical axis direction of the laser light with respect to the focus position of the laser light. It is explanatory drawing equivalent to FIG. 10 in case the whole reflectance variable object is a material from which a reflectance changes. An explanatory diagram showing a waveform of a peak value of a reproduction signal with respect to a moving position when the reflectance variable object is moved with respect to the focus position of the laser light after changing the reflectance of the reflectance variable object by laser light reflection. It is. Focus error signal, X-direction error signal, and Y-direction error for the moving position when the reflectance-variable object is moved with respect to the focus position of the laser light after changing the reflectance of the variable-reflectance object by laser light reflection It is explanatory drawing which showed the waveform of the peak value of a signal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Focus position deviation detection apparatus 10 ... Stage 12 ... Standing member 14 ... Mounting rod 18 ... Optical head 20 ... Table 22 ... Movement Body 24 ··· Motor 24a · · · Encoder 26 · · · Frame 28 · · · Moving body 30 · · · Shaft 32 · · · Motor 32a · · · Encoder 34 · · · Frame 36 ··· Base 38 ··· Motor 38a · · · Encoder 100 · · · Signal amplification circuit 102 · · · Reproduction signal generation circuit 104 · · · Focus error signal generation circuit 106 · · · X direction error signal Generation circuit 108 ... Y-direction error signal generation circuit 110 ... Signal switching circuit 112 ... A / D converter 120 ... Laser drive circuit A
122... Laser driving circuit B
200... Z direction moving motor control circuit 202... Z direction position detecting circuit 210... X direction moving motor control circuit 212... X direction position detecting circuit 220. ..Y direction position detection circuit 300 ... controller 302 ... display device 304 ... input device

Claims (4)

Optical axis receives a plurality of laser emitting device to a laser beam irradiated by focused by the same lens, the reflected light of the plurality of laser light the irradiation is substantially the same, and outputs a light reception signal based on the reflected light In a laser beam focus position deviation detecting device for detecting a deviation between a laser beam focus position designated by an optical head having a light receiving element and a laser beam focus position other than the designated one ,
When the laser beam is focused with a lens and irradiated with a predetermined intensity for a predetermined time, a reflectivity variable object including a material in which the reflectivity of the portion where the laser beam is focused is changed,
A table for setting the reflectance variable object;
Driving means for the focus position of the plurality of laser beams to drive the table or the optical head so as to move in the optical axis direction of the variable reflectance object and relatively least said plurality of laser beams,
Drive amount detection means for detecting a drive amount by the drive means;
A peak value acquisition means for generating an adjustment signal using a light reception signal output from the light receiving element of the optical head, and acquiring a peak value of the adjustment signal;
The specified laser beam of the optical head is irradiated to the reflectivity variable object with an intensity that does not change the reflectivity of the spot where the specified laser beam is focused, and the focus position of the specified laser beam is adjusted by the driving means. The specified laser beam is moved in the optical axis direction, the peak value of the adjustment signal is acquired by the peak value acquisition means, and the location where the specified laser beam is focused based on the peak value is the reflectivity variable object. Designated laser beam irradiation position adjusting means to be set to
Where the reflectivity variable object is irradiated with the laser beam specified by the optical head to the reflectivity variable object at an intensity at which the reflectivity of the spot where the specified laser beam is focused is changed A reflectance change point creating means for creating
A laser beam other than that specified by the optical head is irradiated to the variable reflectivity object at an intensity that does not change the reflectivity of the portion where the laser beam other than the specified beam is focused, and the drive unit does not specify the beam. The laser beam focus position is moved in the optical axis direction of the laser beam other than the specified one, and the peak value of the adjustment signal is adjusted by the peak value acquisition unit in accordance with the drive amount detected by the drive amount detection unit. And a deviation detection means for detecting a deviation between the focus position of the laser beam designated by the optical head and the focus position of the laser light other than the designation based on the obtained peak value. A focus position deviation detection device for laser light. The drive means has two directions in which the focus positions of the plurality of laser beams of the optical head are perpendicular to the optical axis directions of the plurality of laser beams of the optical head and are orthogonal to each other, relative to the reflectance variable object. Means for driving the table or the optical head to move to
The drive amount detection means includes means for detecting drive amounts in the two directions;
The deviation detecting means moves the focus positions of the laser beams other than those specified by the driving means in the two directions, respectively, to correspond to the driving amounts in the two directions detected by the driving amount detecting means, respectively. The peak value of the adjustment signal is acquired by the peak value acquisition means, and based on the acquired peak value, the specified laser beam focus position in the two directions and the laser beam focus position other than the specified 2. The laser beam focus position deviation detecting device according to claim 1 , further comprising means for detecting a deviation of the laser beam. When the light receiving element of the optical head is composed of divided light receiving elements, the peak value acquisition means creates a plurality of adjustment signals and acquires the peak values of the selected adjustment signals. the laser beam focus position deviation detecting system according to claim 1 or claim 2, wherein the at. A laser emitter that irradiates and focuses a plurality of laser beams having substantially the same optical axis by the same lens, and receives reflected light of the plurality of irradiated laser beams, and outputs a received light signal based on the reflected light In a laser beam focus position adjusting method for adjusting a laser beam focus position other than the specified laser beam focus position to a specified laser beam focus position of an optical head having a light receiving element,
When a laser beam is focused by a lens and irradiated for a predetermined time at a predetermined intensity, the laser specified by the optical head is applied to a variable reflectance object containing a material that changes the reflectivity of the portion where the laser beam is focused. Light is irradiated onto the variable reflectivity object at an intensity that does not change the reflectivity of the portion where the designated laser beam is focused, and the focus positions of the plurality of laser beams are at least relative to the reflectivity variable object. The focus position of the designated laser beam is driven in the optical axis direction of the designated laser beam by the drive means for driving the reflectivity variable object or the optical head so as to move in the optical axis direction of the laser beam, and The peak value of the adjustment signal created using the light reception signal output from the light receiving element of the optical head is obtained, and the location where the designated laser beam is focused is set in the reflectivity variable object based on the peak value. Designation laser beam irradiation position adjustment step of at,
Where the reflectivity variable object is irradiated with the laser beam specified by the optical head to the reflectivity variable object at an intensity at which the reflectivity of the spot where the specified laser beam is focused is changed A reflectance change location creation step for creating
A laser beam other than that specified by the optical head is irradiated to the reflectivity variable object with an intensity that does not change the reflectivity of the portion where the laser beam other than the specified focus is focused, and the variable reflectivity object or the light The drive means for driving the head moves the focus position of the laser light other than the designated while detecting the drive amount in the optical axis direction of the laser light other than the designated, and corresponds to the detected drive amount. The crest value of the adjustment signal created using the light reception signal output from the light receiving element of the light head is acquired, and based on the acquired crest value, the focus position of the laser beam designated by the optical head and the A focus position adjusting step for detecting a deviation from the focus position of the laser beam other than the designated laser beam and adjusting the focus position of the laser beam other than the designated laser beam so that the detected deviation is eliminated. The laser beam focus position adjusting method characterized.

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