JP3561735B2 - Multi-beam optical disc playback device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a multi-beam type optical disk reproducing apparatus, and particularly to an optical disk such as a CD-ROM, a CD-WO, a DVD, a DVD-ROM, a DVD-RAM, an MO, an LD, and the like. The present invention relates to a multi-beam type optical disc reproducing apparatus in which separate light beams are simultaneously irradiated, and recording data recorded on a track irradiated with each light beam is read by a recording data reproducing system from a detection output of each return beam.
[0002]
[Prior art]
As one of the methods for reading recorded data from a CD-ROM at high speed, there is a multi-beam method. This is because a plurality of adjacent tracks on an optical disk on which tracks are formed in a spiral shape are simultaneously irradiated with separate light beams, and from the detection output of each return beam, each light beam is irradiated by a recording data reproducing system. The recorded data recorded on the track is read, and the read data is output in the recording order while preventing duplication and omission.
[0003]
The configuration of the multi-beam type CD-ROM reproducing device will be described with reference to FIG.
In FIG. 5, reference numeral 1 denotes a CD-ROM in which tracks on which data is recorded are formed in a spiral shape (the inner left side in FIG. 5 and the outer right side in FIG. 5). The CD-ROM 1 is rotated at a constant linear speed by a spindle motor (not shown). Reference numeral 2 denotes a multi-beam type optical pickup capable of irradiating five light beams, and moves from the inner peripheral side to the outer peripheral side while rotating relative to the CD-ROM 1 and as recording data is read. I do. The optical pickup 2 separately emits light beams 3 for n = 5 adjacent tracks on the CD-ROM 1.₁~ 3₅At the same time and each return beam is a separate photodetector PD₁~ PD₅And outputs a photocurrent as a detection signal.
[0004]
4 of the optical pickups 2₁~ 4₅Denotes a laser diode, and a laser beam 3₁~ 3₅Emits light. Reference numeral 6 denotes a beam splitter in which two right-angle prisms are bonded, 7 denotes a collimator lens that converts each beam from diffused light to parallel light, and 8 denotes a light beam 3 that has passed through the beam splitter 6 and the collimator lens 7.₁~ 3₅Is an objective lens for focusing on the signal surface 1A of the CD-ROM 1, and the optical axis of the objective lens 8 crosses the signal surface 1A perpendicularly. Numeral 9 moves the objective lens 8 in the vertical direction of the CD-ROM 1 following the surface deflection of the CD-ROM 1,₁~ 3₅A focus actuator 10 for maintaining a focused state with respect to the signal surface 1A of the CD-ROM 1 moves the objective lens 8 in the radial direction of the CD-ROM 1 in accordance with the fluctuation of the center of the CD-ROM 1.₁~ 3₅This is a tracking actuator for causing the track to correctly trace a track. The focus actuator 9 and the tracking actuator 10 are individually driven by a servo circuit described later.
[0005]
PD₁~ PD₅Are the light beams 3₁~ 3₅And a photodetector individually provided in response to the above, and outputs a photocurrent proportional to the amount of received light. Light beam 3₁~ 3₅Each return beam reflected by the signal surface 1A of the CD-ROM 1 passes through the objective lens 8 and the collimator lens 7, then is reflected by the beam splitter 6, and passes through an optical system (not shown) such as a cylindrical lens and a detector lens. After that, individual photo detector PD₁~ PD₅Incident on. Photo detector PD₁, PD₂, PD₄, PD₅Is the photocurrent I proportional to the amount of received light₁, I₂, I₄, I₅To the light beam 3₁~ 3₅Are output as detection signals of the respective return beams. Photo detector PD₃Is a four-division photodiode similar to that used in an ordinary one-beam type optical pickup, and a photocurrent I which is proportional to the amount of light received for each of the A, B, C, and D division diodes.₃-A, I₃-B, I₃-C, I₃-D is output.
[0006]
Reference numeral 11 denotes a thread motor for moving the optical pickup 2 in the radial direction of the CD-ROM 1 during reproduction or search, and is driven by a servo circuit to move the optical pickup 2 to a desired position in a forward direction or a reverse direction during a search. During reproduction, the optical pickup 2 is gradually moved in the forward direction as the reproduction of the CD-ROM 1 progresses.
[0007]
Reference numeral 20 denotes a recording data reproducing system, and each photodetector PD of the optical pickup 2₁~ PD₅From each received light output₁~ 3₅Is read out and serially output in the order of recording on the CD-ROM 1 while preventing duplication and omission. Of the recorded data reproducing system 20, 21₁, 21₂, 21₄, 21₅Is a photo detector PD₁, PD₂, PD₄, PD₅Photocurrent I output from₁, I₂, I₄, I₅Is converted into a current / voltage by the light beam 3₁, 3₂, 3₄, 3₅RF signal RF corresponding to₁, RF₂, RF₄, RF₅Current / voltage converter (I / V) that outputs₃-A, 21₃-B, 21₃-C, 21₃−D is a photodetector PD₃Photocurrent I output from₃-A, I₃-B, I₃-C, I₃-D is converted to current / voltage, and the voltage value V_A, V_B, V_C, V_DIs a current / voltage converter (I / V).
[0008]
Reference numeral 22 denotes an arithmetic unit, and (V_A+ V_B+ V_C+ V_D) To calculate the light beam 3₃RF signal RF corresponding to₃Or (V_A+ V_C)-(V_B+ V_D) To form a focus error signal or (V_A+ V_B)-(V_C+ V_D) To form a tracking error signal. FIG. 6 shows a specific configuration of the arithmetic unit 22. 22 of the operation units 22₁Is (V_A+ V_B+ V_C+ V_D) To calculate the light beam 3₃RF signal RF corresponding to₃Adder that outputs₂Is (V_A+ V_C)-(V_B+ V_D22) an adder / subtracter that performs the operation of (2) and outputs a focus error signal;₃Is (V_A+ V_B)-(V_C+ V_D) Is an adder / subtracter that outputs the tracking error signal TE by performing the operation of (2).
[0009]
Reference numeral 23 denotes a servo circuit that performs focus servo control, tracking servo control, and thread servo control, and drives the focus actuator 9 based on the focus error signal FE input from the arithmetic unit 22 so that the focus error signal FE becomes zero. Light beam 3₁~ 3₅Is focused on the signal surface 1A, and the tracking actuator 10 is driven based on the tracking error signal TE input from the arithmetic unit 22 so that the tracking error signal TE becomes zero.₁~ 3₅Respectively follow (on-track) the corresponding track.
[0010]
It should be noted that variations in the optical system of the optical pickup 2 and the photodetector PD₃, Current / voltage converter 21₃-A to 21₃−D, adder / subtractor 22₂The adder-subtractor 22₂The focus error signal output by the light beam 3₃Does not become zero even when the focus is completely focused on the signal surface 1A of the CD-ROM 1, and each set has a different offset amount. The focus servo system controls the focus error signal FE input to the servo circuit 23 to be zero.₂Is input to the servo circuit 23 as it is, the light beam 3₃May not be in focus with respect to the signal surface 1A, and the error rate of the data read from the CD-ROM 1 may be too large to make it impossible to reproduce the data.
[0011]
For this reason, an offset adjustment function has conventionally been added to the focus servo system. That is, the arithmetic unit 22 has a variable focus bias voltage V under the control of a system controller described later._fBias voltage generating circuit 22 that generates₄And the adder / subtracter 22₂Output the focus error signal to the focus bias voltage V_fAdder 22 that adds focus error signal FE to generate focus error signal FE₅And an appropriate focus bias voltage V for each set._fIs applied to the focus bias system, thereby canceling the offset error of the optical system and the circuit system, and the light beam 3₃Can be focused on the signal surface 1A.
[0012]
Returning to FIG.₁~ 24₅Are the light beams 3₁~ 3₅RF signal RF to compensate for high-frequency attenuation due to the spatial transfer frequency characteristic (MTF) of₁~ RF₅Is a waveform equalizing circuit that raises the high-frequency component of the signal and suppresses the occurrence of intersymbol interference. The waveform equalizing circuit 24₃RF signal input to RF₃Or the waveform equalization circuit 24₃Signal RF output from₃Is input to the servo circuit 23. When turning on the focus servo, the servo circuit 23 determines the timing at which the value of the focus error signal FE is in the negative feedback region of the focus servo while performing a focus search operation, and turns on the servo. When the tracking servo is turned on, the RF signal RF₃Light beam 3 using₃Is determined to enter the negative feedback area of the tracking servo, and the servo is turned on.
[0013]
26₁~ 26₅Are first signal processing circuits, each of which is an RF signal RF₁~ RF₅To perform binarization, clock recovery using a PLL circuit, bit demodulation, frame synchronization detection, EFM demodulation, and subcode demodulation, and data after EFM demodulation (including P and Q parities).₁~ DATA₅A-time (Absolute-time; absolute time) data AT of the corresponding subcode Q channel in units of one block (a unit for 98 frames in which one subcode frame is completed).₁~ AT₅Output with First signal processing circuit 26₁~ 26₅Is the demodulated data DATA₁~ DATA₅Are serially output one symbol (8 bits) at a time. First signal processing circuit 26₃A-time data AT output from₃Is input to a system controller 50 described later. RF signal RF₃First signal processing circuit 26 of the system₃Has a built-in CLV control circuit (not shown) for detecting a frame synchronization signal at fixed time intervals, and performs CLV control on a spindle motor drive circuit (not shown) to read the CD-ROM 1. Rotate at a constant linear velocity.
[0014]
First signal processing circuit 26₁~ 26₅Detects the frame synchronization and sends an H-level frame synchronization detection signal FS to the system controller.₁~ FS₅Is output. This frame synchronization detection signal FS₁~ FS₅Is used, for example, to determine whether or not the track jump has been completed. Further, the third signal processing circuit 26₃Has a built-in jitter amount measurement circuit (not shown) for measuring the amount of jitter of the binarized RF signal, and has the measured jitter amount data JD₃Is output to the system controller. First signal processing circuit 26₃Data JD input from₃Is used for focus bias adjustment.
[0015]
30 is each first signal processing circuit 26₁~ 26₅Is a parallel / serial conversion unit (P / S) that inputs data in units of one block output from the unit in parallel and outputs the data serially in the recording order without duplication or omission. FIG. 7 shows a specific configuration of the parallel / serial conversion unit 30. In FIG. 7, 32₁~ 32₅Each have two storage areas, a first area and a second area, and the first signal processing circuit 26₁~ 26₅And a first signal processing circuit 26.₁~ 26₅Data output from₁~ DATA₅Is stored in one of the storage areas. The first area and the second area have a sufficient number of blocks of data DATA.₁~ DATA₅Has the capacity to store 33₁~ 33₅Each have two storage areas, a first area and a second area, and the first signal processing circuit 26₁~ 26₅And a first signal processing circuit 26.₁~ 26₅A-time data AT output from₁~ AT₅Are respectively the corresponding data DATA₁~ DATA₅Memory 32₁~ 32₅Address A indicating the position stored in_1S~ A_5s(Or a_1s~ A_5s) And last address A_1e~ A_5e(Or a_1e~ A_5e) Is stored in one of the storage areas. The first area and the second area have a sufficient number of A-time data AT.₁~ AT₅Has the capacity to store
[0016]
31₁~ 31₅Are the first signal processing circuits 26₁~ 26₅And a first signal processing circuit 26.₁~ 26₅Data output from₁~ DATA₅The memory 32₁~ 32₅In the first area or the second area of the A-time data AT₁~ AT₅The corresponding data DATA₁~ DATA₅Memory 32₁~ 32₅Address A indicating the position stored in_1s~ A_5S(Or a_1s~ A_5s) And last address A_1e~ A_5e(Or a_1e~ A_5e) And memory 33₁~ 33₅Is written to the first area or the second area.
[0017]
For example, the write controller 31_f(F = 1 to 5) is the memory 32_f15 blocks of data DATA in the first area of_f(1)-DATA_f(15) is written, and data DATA for 15 blocks is written in the second area._f(16)-DATA_fMemory 32 when (30) is written_fAnd 33_fIs shown in FIG. Memory 33_fIn the first area, data DATA_f(1)-DATA_fThe A-time data of each block of (15) is written as, for example, 23 minutes 40 seconds 60 frames to 23 minutes 40 seconds 74 frames, and the memory 32_fDATA in the first area of_f(1)-DATA_fStart address A indicating the storage position of (15)_fS(1) and last address A_fe(1) to start address A_fS(15) and last address A_fe(15) is written. Memory 33_fIn the second area, data DATA_f(16)-DATA_fThe A-time data relating to each block of (30) is written as, for example, 23 minutes 41 seconds 48 frames to 23 minutes 41 seconds 62 frames, and the memory 32_fDATA in the second area of_f(16)-DATA_fStart address a indicating the storage position of (30)_fS(1) and last address a_fe(1) to start address a_fS(15) and last address a_fe(15) is written.
[0018]
Reference numeral 34 denotes a read controller, and a memory 33₁~ 33₅A-time data AT stored in₁~ AT₅And start address A_1s~ A_5s(Or a_1s~ A_5s) And last address A_1e~ A_5e(Or a_1e~ A_5e), The memory 32₁~ 32₅Data stored in₁~ DATA₅Are read out in the recording order (A-time order) on the CD-ROM 1 while preventing duplication and omission from occurring, and are output serially one symbol at a time. Write controller 31₁~ 31₅The specific operation of the read controller 34 will be described later.
[0019]
Returning to FIG. 5, reference numeral 40 denotes a second signal processing circuit which receives data serially output from the parallel / serial conversion unit 30, performs descrambling for each block, and then performs error detection based on the CIRC code. / Error (error detection / correction by P parity, deinterleaving, error detection / correction by Q parity) to demodulate Lch data and Rch data conforming to the CD-DA standard. Based on the ROM standard, CD-ROM data is demodulated by performing synchronization detection, descramble, header detection, error detection / correction using EDC and ECC codes, and outputs the data to an external host computer.
[0020]
Reference numeral 50 denotes a system controller having a microcomputer configuration, which supplies a search command to the servo circuit 23 at the time of a search to the servo circuit 23, drives the thread motor 11 to search, and moves the optical pickup 2 in the forward direction or the reverse direction of the CD-ROM 1. At the time of reproduction, various servo-on commands are given to the servo circuit 23 to reproduce the light beam 3₁~ 3₅Is focused on the signal surface 1A of the CD-ROM 1 and five tracks adjacent to each other are turned on. Then, every time the recording data is read from each track for approximately one rotation of the CD-ROM 1, a track jump command for three tracks is given in the forward direction to cause a track jump.
[0021]
Also, when the reproduction of the CD-ROM 1 is started, the system controller 50 sends the first signal processing circuit 26₃Data JD input from₃While monitoring the focus bias voltage generation circuit 22₄To control the focus bias voltage V_fAnd the jitter amount data JD₃Where V is minimum_fAdjust the focus bias by fixing the value of.
[0022]
Next, the operation of the above-described CD-ROM reproducing apparatus will be described with reference to FIGS. FIG. 9 is an explanatory diagram of the data reproducing operation, and shows a relative positional relationship between the CD-ROM 1 and the optical pickup 2 as viewed from the signal surface 1A side of the CD-ROM 1. FIG.₁~ 33₅FIG. 11 is a flowchart showing focus bias adjustment processing by the system controller 50.
It is assumed that the CD-ROM 1 is rotated at a constant linear velocity by CLV control, and that the focus servo is also turned on in advance. The number n of light beams is set to 5.
[0023]
(1) Focus bias adjustment
When the A-time of the reproduction start point for the CD-ROM 1 is designated by the host computer (not shown) as, for example, 23 minutes 41 seconds 00 frames, the system controller 50 displays the A-time of the reproduction start point on the CD-ROM 1 The position of the track including the time is determined and set as x (see FIG. 9). Then, first, a search command is given to the servo circuit 23, and the light beam 3₁The optical pickup 2 is moved so that the position of the optical pickup 2 comes to the position of the track (x-6).₄To control V_fAfter initialization to = 0V, a tracking servo ON command and a thread servo ON command are given to the servo circuit 23 to turn on the tracking servo and the thread servo. As a result, the light beam 3 emitted from the optical pickup 2₁~ 3₅Focuses and tracks on tracks (x-6) to (x-1) (see I in FIG. 9). However, since the focus bias has not been adjusted yet, the light beam 3₁~ 3₅Are not in the optimum focusing state.
[0024]
Each light beam 3₁~ 3₅Is reflected by the signal surface 1A of the CD-ROM 1, the return light beam is a photodetector PD.₁~ PD₅Receives light and the photocurrent I₁~ I₅And the photo detector PD₁, PD₂, PD₄, PD₅Photocurrent I from₁, I₂, I₄, I₅Is the current / voltage converter 21₁, 21₂, 21₄, 21₅Current / voltage conversion by the RF signal RF₁, RF₂, RF₄, RF₅Are formed, and the waveform equalizing circuit 24₁, 24₂, 24₄, 24₅The first signal processing circuit 26₁, 26₂, 26₄, 26₅Is entered. Also, photo detector PD₃Photocurrent I from₃-A to I₃-D is the current / voltage converter 21₃-A to 21₃The voltage value V_A~ V_DAnd the adder 22 of the arithmetic unit 22₁RF signal RF₃Is formed. Then, the waveform equalizing circuit 24₃The first signal processing circuit 26₃Is entered.
[0025]
First signal processing circuit 26₁~ 26₅Are the input RF signals RF₁~ RF₅On the other hand, binarization, clock recovery using a PLL circuit, bit demodulation, frame synchronization detection, EFM demodulation, and subcode demodulation are performed, and the data after EFM demodulation (including P and Q parities) DATA₁~ DATA₅Is the A-time data AT of the subcode Q channel corresponding to one block unit.₁~ AT₅Output with First signal processing circuit 26₁~ 26₅Is the demodulated data DATA₁~ DATA₅Are serially output one symbol (8 bits) at a time. Also, the first signal processing circuit 26₁~ 26₅Detects a frame synchronization signal, and outputs an H level frame synchronization detection signal FS.₁~ FS₅And the first signal processing circuit 26₃Measures the amount of jitter of the binarized RF signal and outputs the jitter amount data JD₃Is output to the system controller 50. Also, the first signal processing circuit 26₃Is A-time data AT₃Is output to the system controller 50.
[0026]
The system controller 50 performs a search operation to control each light beam 3 of the optical pickup 2.₁~ 3₅After on-tracking on tracks (x-6) to (x-2), focus bias adjustment processing is performed according to FIG. First, V_f= 0V, the first signal processing circuit 26₃Jitter data JD measured at₃Is read and stored in a built-in memory (not shown) as jd (0) (step S10). Next, the focus bias voltage generation circuit 22₄And V_fIs increased from 0 V by plus ΔV (ΔV is a positive value), and the jitter amount data JD at this time is increased.₃Is read and stored as jd (+1) in a built-in memory (not shown). Furthermore, V_fIs reduced from 0 V to the minus side by ΔV, and the jitter amount data JD at this time is reduced.₃Is read and stored as jd (-1) in a built-in memory (not shown) (step S11).
[0027]
Then, the magnitudes of jd (+1), jd (0), and jd (-1) are compared, and if jd (+1)> jd (0) <jd (-1) (YES in step S12), V_fIs 0 V, the jitter amount is the lowest, and it is considered that the focus offset was originally almost 0. Therefore, the focus bias voltage generation circuit 22₄And V_fIs set to 0 V, and the adjustment is completed (step S13).
If jd (+1) <jd (0) <jd (-1) (YES in step S14), k is set to 2 (step S15), and V_f= (+ 2) · ΔV, and the jitter amount data JD at this time₃Is read to jd (+2) (step S16). If jd (+2)> jd (+1) <jd (0) (YES in step S17), V_fIs (+1) · ΔV, the jitter amount is the lowest,₂Since it is considered that the focus offset seen at the output point of (1) was originally approximately (+1) · (−ΔV), the focus bias voltage generation circuit 22₄And V_fIs set to (+1) · ΔV, and the adjustment is completed (step S18).
[0028]
If jd (+2)> jd (+1) <jd (0) is not satisfied (NO in step S17), k is incremented to 3 (step S19), and the process returns to step S16 to repeat the same processing, and a certain k If jd (+ k)> jd {+ (k-1)} <jd {+ (k-2)} (YES in step S17), V_fIs {+ (k−1)} · ΔV, the jitter amount is the lowest, and it is considered that the focus offset was originally approximately {+ (k−1)} · (−ΔV). Circuit 22₄And V_fIs set to {+ (k−1)} · ΔV, and the adjustment is completed (step S18).
[0029]
If jd (+1) <jd (0) <jd (-1) is not satisfied in step S14, k is set to 2 (step S20), and V_f= (− 2) · ΔV, and the jitter amount data JD at this time₃Is read to jd (-2) (step S21). If jd (−2)> jd (−1) <jd (0) (YES in step S22), V_fIs (−1) · ΔV, the jitter amount is the lowest,₂Since it is considered that the focus offset seen at the output point of (1) was originally substantially (-1). (-. DELTA.V), the focus bias voltage generation circuit 22₄And V_fIs set to (−1) · ΔV, and the adjustment is completed (step S23).
[0030]
If jd (−2)> jd (−1) <jd (0) is not satisfied (NO in step S22), k is incremented to 3 (step S24), and the same process is repeated to obtain a certain value of k. , Jd (−k)> jd {− (k−1)} <jd {− (k−2)} (YES in step S22),_fIs {− (k−1)} · ΔV, the jitter amount is the minimum, and the adder / subtracter 22₂It is considered that the focus offset seen at the output point is originally approximately {− (k−1)} · (−ΔV), so the focus bias voltage generation circuit 22₄And V_fIs set to {− (k−1)} · ΔV, and the adjustment is completed (step S23).
When the focus bias adjustment is completed in this manner, the light beam 3₃Is completely focused on the signal surface 1A (in FIG. 5, the light beam 3₃Focus point P₃Coincides with the signal surface 1A), and the other light beams 3₁, 3₂, 3₄, 3₅Is also close to a perfect focus state (in FIG. 5, the light beam 3₁, 3₂, 3₄, 3₅Focus point P₁, P₂, P₄, P₅Comes near the signal plane 1A).
[0031]
(2) Data reproduction operation (see FIGS. 9 and 10)
When the focus bias adjustment is completed as described above, the first signal processing circuit 26₃Latest A-time data AT input from₃From the A-time data indicated by A and the A-time at the reproduction start point designated by the host computer,₁A track jump direction is determined by setting the track jump direction for turning on the track (x-1) on the inner circumference side of one track x including the A-time of the reproduction start point, and the number of tracks to be jumped.
If the optical pickup 2 is at the position II in FIG. 9 when the focus bias adjustment is completed, the optical pickup 2 is caused to make a track jump by four tracks in the forward direction, and the light beam 3₁~ 3₅On tracks (x-1) to (x + 3), respectively (see III in FIG. 9), and the photodetector PD₁~ First signal processing circuit 26₁, Photodetector PD₂~ First signal processing circuit 26₂, Photodetector PD₃~ First signal processing circuit 26₃, Photodetector PD₄~ First signal processing circuit 26₄, Photodetector PD₅~ First signal processing circuit 26₅, The simultaneous reading of the recording data of the tracks (x-1) to (x + 3) is started, and the first signal processing circuits 26₁~ 26₅To H level frame synchronization detection signal FS₁~ FS₅Is input to the parallel / serial conversion unit 30.
[0032]
Write controller 31 that has received a write / read command via read controller 34₁~ 31₅Are respectively the first signal processing circuit 26₁~ 26₅Data output from₁~ DATA₅Is stored in the memory 32 for each block.₁~ 32₅In the first area of the memory 33 and the memory 33₁~ 33₅Data DATA in the first area of₁~ DATA₅A-time data AT corresponding to₁~ AT₅And memory 32₁~ 32₅Address A at_1S~ A_5S, Last address A_1e~ A_5eAre written in pairs (see FIG. 8). In the case of FIG.₁~ 33₅23:40:60 frame, 23:41:00 frame, 23:41:15 frame, 23:41:30 frame, 23:41:45 frame, and 23:41:45 frame and later are written as A-time data in the first area of (See FIG. 10).
[0033]
On the other hand, the read controller 34 receiving the write / read command₁~ 33₅Of the memory 33 by referring to the contents of the first area in which writing is performed this time.₅A-time immediately before the head A-time data of the first area of the₄Of the memory 33₄A-time immediately before the head A-time data of the first area of the₃Of the memory 33₃A-time immediately before the head A-time data of the first area of the₂Of the memory 33₂A-time immediately before the head A-time data of the first area of the₁Then, it is checked whether or not the data read by each of the reading systems has no missing data.
[0034]
When reading by the optical pickup 2 is performed for approximately one rotation (actually, slightly more than one rotation) and the process proceeds to the position IV in FIG.₁~ 33₅The contents of the first area are as shown in FIG.₁~ 3₅Since the data read by each of the systems has no missing data, the reading controller 34₁~ 31₅To the system controller 50, to give a track jump command to the system controller 50.₁~ 33₅The memory 32 refers to the A-time data, the start address, and the end address stored in the first area in which the A-time data is written.₁~ 32₅Of which, this time DATA₁~ DATA₅The data is read out in the order of A-time from the data corresponding to the youngest A-time in the first area in which is written, and is output to the second signal processing circuit 40. Here, frames from 23 minutes 40 seconds 60 frames to 23 minutes 41 seconds 59 frames are output. Originally, the A-time at the playback start point specified by the host computer is 23:41:00, so that it is output immediately before the playback start point.
[0035]
The second signal processing circuit 40 receives the data serially output from the parallel / serial conversion unit 30, first descrambles one block at a time, and then performs error detection / correction based on the CIRC code (error detection / error based on P parity). Correction, deinterleaving, and error detection / correction by Q parity) to demodulate Lch data and Rch data conforming to the CD-DA standard. The CD-ROM data is demodulated by performing error detection / correction using rumble, header detection, EDC and ECC codes, and outputs the data to an external host computer.
[0036]
Write controller 31 that has received the suspend command₁~ 31₅Is the memory 32₁~ 32₅And 33₁~ 33₅Interrupt writing to. Further, the system controller 50 having received the track jump command gives the servo circuit 23 a track jump command of the track number J = 3 in the forward direction, and moves the optical pickup 2 from the position IV to the position V in FIG. Jump, light beam 3₁~ 3₅Are turned on tracks (x + 3) to (x + 7), respectively, and reading of recording data is resumed. Then, the first signal processing circuit 26₁~ 26₅, The H level frame synchronization detection signal FS₁~ FS₅Is output, the track jump completion notification is given to the read controller 34.
[0037]
Upon receiving the track jump completion notification, the read controller 34₁~ 31₅To the write controller 31 that has received the restart instruction.₁~ 31₅Is the first signal processing circuit 26₁~ 26₅Data after track jump output from₁~ DATA₅This time in memory 32₁~ 32₅In the second area of the memory 33 and the memory 33₁~ 33₅Data DATA in the second area of₁~ DATA₅A-time data AT corresponding to₁~ AT₅And memory 32₁~ 32₅Start address a_1S~ A_5S, Last address a_1e~ A_5eAre written in pairs (see FIG. 8). In the case of FIG.₁~ 33₅23:41:48, 23:41:63, 23:42:03, 23:42:18, 23:42:33, and 23:42:33 (See FIG. 10).
[0038]
After giving the restart instruction, the read controller 34₁~ 33₅The memory 33 refers to the contents of the second area in which the current writing is performed.₅A-time immediately before the head A-time data of the second area of the₄Of the memory 33₄A-time immediately before the head A-time data of the second area of the₃Of the memory 33₃A-time immediately before the head A-time data of the second area of the₂Of the memory 33₂A-time immediately before the head A-time data of the second area of the₁Are included in the second area of each light beam 3₁~ 3₅Check whether there is no missing data in each system.
[0039]
When the reading by the optical pickup 2 is performed for approximately one rotation (actually, slightly more than one rotation) and proceeds to the position VI in FIG.₁~ 33₅10 becomes as shown in FIG. 10 and the data read by each system for reading does not have any omission.₁~ 31₅To the system controller 50 to give the system controller 50 a track jump command.₁~ 33₅The memory 32 refers to the A-time data, the start address, and the end address stored in the second area in which the A-time data is written.₁~ 32₅Of which, this time DATA₁~ DATA₅Is written in the second area, the data corresponding to the A-time next to the A-time corresponding to the data for one block previously output to the second signal processing circuit 40 last time is in A-time order. The data is read and output to the second signal processing circuit 40. Here, frames from 23 minutes 41 seconds 60 frames to 23 minutes 42 seconds 47 frames are output.
[0040]
Write controller 31 that has received the suspend command₁~ 31₅Is the memory 32₁~ 32₅And 33₁~ 33₅9, the system controller 50 having received the track jump command causes the optical pickup 2 to make a track jump from the position VI to the position VII in FIG.₁~ 3₅On the tracks (x + 7) to (x + 11) to restart reading the recording data, and the first signal processing circuit 26₁~ 26₅Of all frame synchronization detection signals FS of H level₁~ FS₅Is output to the read controller 34 at the point in time when is output.
[0041]
The write controller 31 that has received the track jump completion notification via the read controller 34₁~ 31₅Is the first signal processing circuit 26₁~ 26₅Data after track jump output from₁~ DATA₅This time in memory 32₁~ 32₅In the first area of the memory 33 and the memory 33₁~ 33₅Data DATA in the first area of₁~ DATA₅A-time data AT corresponding to₁~ AT₅And memory 32₁~ 32₅Address A at_1S~ A_5S, Last address A_1e~ A_5eWrite in pairs. On the other hand, the read controller 34₁~ 33₅When there is no missing A-time stored in the first area of the memory 32 and all the A-time are in a continuous state, the memory 32₁~ 32₅In the first area, data is sequentially sorted in A-time order from the data corresponding to the A-time next to the A-time corresponding to the data of one block last output to the second signal processing circuit 40 last time. Read and output. Thereafter, by repeating the same operation, desired recording data is read from the CD-ROM 1 at high speed in the recording order without duplication or omission.
[0042]
Note that when the track jumps from the position IV in FIG. 9, the number of tracks to be jumped is not set to 4, but the light beam 3₅Light beam 3 on the track (x + 3) from which data was read by₁In this case, the number of tracks to be jumped is set to three. The reason is that if the number of tracks to be jumped is set to 4, the light beam 3₅This is because data such as A-time = 23: 41: 60 frame, 23:41:61 frame that has not been read yet is lost.
In general, if the number of light beams is n (where n is an integer of 3 or more), reading for approximately one rotation is performed by each light beam, and then track jump in the forward direction by (n-2) beams Thereafter, by repeating the operation of reading the recorded data for approximately one rotation again, the CD-ROM 1 is reproduced at high speed.
[0043]
[Problems to be solved by the invention]
By the way, light beam 3₁~ 3₅Are separate laser diodes 4₁~ 4₅Are emitted from the optical pickup 2 and pass through the optical system of the optical pickup 2 independently of each other, so that the beam cross-sectional areas when hitting the signal surface 1A of the CD-ROM 1 are individual. Since the beam cross-sectional area when the light hits the signal surface 1A of the CD-ROM 1 determines the spatial transmission frequency characteristic (MTF) of the light beam, each waveform equalizing circuit 24₁~ 24₅However, there is a problem that the high-frequency compensation characteristics to be set for the individual parts also vary, and the design burden increases.
An object of the present invention is to provide a multi-beam type optical disk reproducing apparatus capable of reducing a design burden in view of the above-mentioned problems of the related art.
It is another object of the present invention to provide a multi-beam type optical disk reproducing apparatus capable of reliably reproducing an optical disk.
[0044]
[Means for Solving the Problems]
In the multi-beam type optical disk reproducing apparatus according to the first aspect of the present invention, n different light beams are simultaneously irradiated on n different tracks (where n is an odd number of 3 or more) of the optical disk, and each return beam is irradiated. High-frequency compensation for forming an RF signal for each light beam from the detection output separately detecting the RF signal, and equalizing the waveform of the RF signal of each light beam by individually provided waveform equalizing means to raise a high-frequency gain. After that, the signal processing means binarizes and demodulates each RF signal and reads the recording data recorded on the track irradiated with each light beam. One laser beam generated by the means is perpendicularly incident on the diffraction grating, and is composed of 0th-order diffracted light, ± 1st-order diffracted light,... ± mth-order diffracted light (where m is (n-1) / 2). (2m +1) light beams are formed, and these (2m + 1) light beams are focused near the signal surface of the optical disk by an optical system including an objective lens. At this time, the 0th-order diffracted light beam is perpendicular to the optical disk. An optical system is arranged so that the light beam of the + i-order diffracted light and the light beam of the -i-order diffracted light (where i is 1, 2,..., M) among the waveform equalizing means. Pair of waveform equalization means provided with the same waveform equalization characteristicsWhen viewed in the optical axis direction of the objective lens, the signal surface of the optical disk is located at a predetermined position between the focus position of the 0th-order diffracted light beam and the focus position of the ± mth-order diffracted light beam. ,It is characterized by.
[0045]
As a result, of the pair of (2m + 1) light beams, a pair of + i-order diffracted light beam and -i-order diffracted light beam (i = 1, 2,..., M) are converted to 0-order diffracted light beam. The light beam is formed to be completely line-symmetrical with respect to the center, and the signal surface of the optical disc is illuminated completely line-symmetrically with respect to the light beam of the 0th-order diffracted light which is irradiated perpendicularly to the signal surface. Therefore, when the pair of light beams hit the signal surface of the optical disc, the beam cross-sectional area can be made the same, so that the spatial transmission frequency characteristics of the pair of light beams can be made the same. Therefore, the pair of waveform equalizers provided corresponding to the pair of light beams can set the same waveform equalization characteristics to each other, so that when there are a total of (2m + 1) light beams, (m + 1) It is sufficient to design the waveform equalization characteristics only for the individual waveform equalization means.
Further, the 0th, ± 1st,..., ± mth-order diffracted light beams can be brought into a state close to the in-focus state with respect to the signal surface, and a light beam with a poor focus state with respect to the signal surface cannot be formed. Therefore, it is possible to reliably read data from the optical disk.
[0047]
Claims of the invention2The multi-beam type optical disk reproducing apparatus described above includes a focus servo means for moving the objective lens following the surface deflection of the optical disk and always focusing (2m + 1) light beams near the signal surface of the optical disk. The servo means is arranged so that, when viewed in the optical axis direction of the objective lens, the signal surface of the optical disk is located at a predetermined position between the focus position of the 0th-order diffracted light beam and the focus position of the ± mth-order diffracted light beam. The focus bias adjustment is performed.
With this, regardless of the runout of the optical diskThe 0th, ± 1st,..., ± mth order diffracted light beams can always be maintained in a state close to a perfect focus state with respect to the signal surface.Since the occurrence of a light beam with a poor focus state on the signal surface is avoided, data can be reliably read from the optical disk.
[0048]
Claims of the invention3In the described multi-beam type optical disc playback device, NMeasuring means for measuring a jitter amount or an error rate of a binarized RF signal for each of two or more predetermined light beams among the plurality of light beams, wherein the focus servo means is measured by the measuring means. The focus bias adjustment is performed so that the average value of the jitter amount or the error rate is minimized.
This allowsEven if the surface deflection is large, the light beams of the 0th order, ± 1st order,.Since the occurrence of a light beam with a poor focus state on the signal surface is avoided, data can be reliably read from the optical disk.
If the measuring means measures the jitter amount or the error rate of the binarized RF signal for each of the n light beams, the focus state of each light beam on the signal surface of the optical disk can be easily determined. Optimized for optical discbigThe optimum focus state is maintained irrespective of the surface shake, so that data can be more reliably read from the optical disc.
[0049]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described with reference to FIG.
FIG. 1 is a block diagram of a CD-ROM reproducing apparatus according to the present invention, and the same components as those in FIG. 5 are denoted by the same reference numerals.
In FIG. 1, reference numeral 1 denotes a CD-ROM in which tracks on which data is recorded are formed in a spiral shape (the left side in FIG. 1 is the inner side, and the right side is the outer side). The CD-ROM 1 is rotated at a constant linear speed by a spindle motor (not shown). Numeral 2A denotes a multi-beam type optical pickup, in which n = 5 adjacent tracks of the CD-ROM 1 are separately irradiated with light beams 3 respectively.₁~ 3₅At the same time and each return beam is a separate photodetector PD₁~ PD₅And outputs a photocurrent as a detection signal.
[0050]
A laser diode 4 emits a laser beam 3 in the optical pickup 2A. Reference numeral 5 denotes a light beam 3 which is arranged perpendicularly to the optical axis of the laser diode 4, diffracts the laser beam 3, and is a second-order diffracted light.₁, The first-order diffracted light beam 3₂, The light beam 3 which is the zero-order diffracted light₃, The light beam 3 which is the + 1st-order diffracted light₄, + 2nd-order diffracted light beam 3₅(Diffraction grating), 6 is a beam splitter in which two right-angle prisms are bonded, 7 is a collimator lens that converts each beam from diffused light to parallel light, 8 is light that has passed through the beam splitter 6 and the collimator lens 7 Beam 3₁~ 3₅Is an objective lens for focusing on the signal surface 1A of the CD-ROM 1, and the optical axis of the objective lens 8 crosses the signal surface 1A perpendicularly.
[0051]
Numeral 9 moves the objective lens 8 in the vertical direction of the CD-ROM 1 following the surface deflection of the CD-ROM 1,₁~ 3₅A focus actuator 10 for maintaining a focused state with respect to the signal surface 1A of the CD-ROM 1 moves the objective lens 8 in the radial direction of the CD-ROM 1 in accordance with the fluctuation of the center of the CD-ROM 1.₁~ 3₅This is a tracking actuator for causing the track to correctly trace a track. The focus actuator 9 and the tracking actuator 10 are individually driven by a servo circuit described later.
[0052]
PD₁~ PD₅Are the light beams 3₁~ 3₅And a photodetector individually provided in response to the above, and outputs a photocurrent proportional to the amount of received light. Light beam 3₁~ 3₅Each return beam reflected by the signal surface 1A of the CD-ROM 1 passes through the objective lens 8 and the collimator lens 7, then is reflected by the beam splitter 6, and passes through an optical system (not shown) such as a cylindrical lens and a detector lens. After that, individual photo detector PD₁~ PD₅Incident on.
[0053]
Here, an optical axis of an optical system including a beam splitter 6, a collimator lens 7, an objective lens 8, a cylindrical lens, a detector lens, and the like, and a light beam 3 related to the 0th-order diffracted light.₃Of the light beam 3₃Is irradiated perpendicularly to the signal surface 1A of the CD-ROM 1. Light beam 3₃Is completely focused on the signal surface 1A, the other light beam 3₁, 3₂, 3₄, 3₅Is in the vicinity of the signal surface 1A, but is not completely in focus, and the beam cross-sectional area hitting the signal surface 1A is the light beam 3₃Be larger.
However, light beam 3₄And 3₂(3₅And 3₁) Are + 1st-order diffracted light and -1st-order diffracted light (+ 2nd-order diffracted light and -2nd-order diffracted light) when the laser beam 3 is perpendicularly incident on the grating 5, and are the 0th-order diffracted light.₃The light beam 3 of the 0th-order diffracted light which is formed completely symmetrically with respect to the center and is perpendicularly incident on the signal surface 1A₃Irradiating the signal surface 1A of the CD-ROM 1 completely line-symmetrically with respect to the₄And 3₂(3₅And 3₁) Indicates that the beam cross-sectional area when hitting the signal surface 1A is the same, so that the pair of light beams 3₄And 3₂(3₅And 3₁) Have the same spatial transmission frequency characteristics.
[0054]
Photo detector PD₁, PD₂, PD₄, PD₅Is the photocurrent I proportional to the amount of received light₁, I₂, I₄, I₅To the light beam 3₁, 3₂, 3₄, 3₅Are output as detection signals of the respective return beams. Photo detector PD₃Is a four-division photodiode similar to that used in an ordinary one-beam type optical pickup, and a photocurrent I which is proportional to the amount of light received for each of the A, B, C, and D division diodes.₃-A, I₃-B, I₃-C, I₃-D is output.
[0055]
Reference numeral 11 denotes a thread motor for moving the optical pickup 2A in the radial direction of the CD-ROM 1 during reproduction or search, and is driven by a servo circuit to move the optical pickup 2A in a forward or reverse direction to a desired position during a search. During the reproduction, the optical pickup 2A is gradually moved in the forward direction as the reproduction of the CD-ROM 1 proceeds.
[0056]
Reference numeral 20A denotes a recording data reproducing system, and each photodetector PD of the optical pickup 2A₁~ PD₅From the received light output of each light beam 3₁~ 3₅At the same time, and outputs the data serially in the recording order without duplication or omission. Of the recorded data reproducing system 20A, 21₁, 21₂, 21₄, 21₅Is a photo detector PD₁, PD₂, PD₄, PD₅Photocurrent I output from₁, I₂, I₄, I₅Is converted into a current / voltage by the light beam 3₁, 3₂, 3₄, 3₅RF signal RF corresponding to₁, RF₂, RF₄, RF₅Current / voltage converter (I / V) that outputs₃-A, 21₃-B, 21₃-C, 21₃−D is a photodetector PD₃Photocurrent I output from₃-A, I₃-B, I₃-C, I₃-D is converted to current / voltage, and the voltage value V_A, V_B, V_C, V_DIs a current / voltage converter (I / V).
[0057]
Reference numeral 22 denotes a calculation unit, as shown in FIG._A+ V_B+ V_C+ V_D) To calculate the light beam 3₃RF signal RF corresponding to₃Or (V_A+ V_C)-(V_B+ V_D), The focus bias voltage V_fIs output as the focus error signal FE, or (V_A+ V_B)-(V_C+ V_D) To output the tracking error signal TE. Reference numeral 23 denotes a servo circuit which performs focus servo control, tracking servo control, and thread servo control.₁~ 3₅Is focused on the signal surface 1A, and the tracking actuator 10 is driven based on the tracking error signal TE so that the tracking error signal TE becomes zero.₁~ 3₅Respectively follow (on-track) the corresponding track.
[0058]
24A₁~ 24A₅Are the light beams 3₁~ 3₅RF signal RF to compensate for high-frequency attenuation due to the spatial transfer frequency characteristic (MTF) of₁~ RF₅Is a waveform equalizing circuit that raises the high-frequency component of the signal and suppresses the occurrence of intersymbol interference. As described above, the light beam 3₁And 3₅Have the same spatial transfer frequency characteristic (MTF), the waveform equalizing circuit 24A₁And 24A₅Are set to have the same waveform equalization characteristics. Similarly, light beam 3₂And 3₄Have the same spatial transfer frequency characteristic (MTF), the waveform equalizing circuit 24A₂And 24A₄Are set to have the same waveform equalization characteristics. Therefore, five waveform equalization circuits 24A₁~ 24A₅It is only necessary to design three types of waveform equalization characteristics.
The other components of the recording data reproducing system 20A are configured exactly the same as in FIG.
[0059]
Next, the operation of the above-described embodiment will be described with reference to FIGS. FIG. 2 is an explanatory diagram showing a data reproducing operation, and shows a relative positional relationship between the CD-ROM 1 and the optical pickup 2A when the CD-ROM 1 is viewed from the signal surface 1A side. It is assumed that the CD-ROM 1 is rotating at a constant linear velocity by the CLV control in advance, and that the focus servo is also turned on. It is assumed that the number of light beams is n = 5.
The data reproducing operation by the multi-beam type CD-ROM reproducing apparatus shown in FIG. 1 is completely the same as that of the apparatus shown in FIG.
[0060]
(1) Focus bias adjustment (see FIGS. 2, 10, and 11)
When the A-time of the reproduction start point for the CD-ROM 1 is designated by the host computer (not shown) as, for example, 23 minutes 41 seconds 00 frames, the system controller 50 displays the A-time of the reproduction start point on the CD-ROM 1 The position of the track including the time is determined and set as x (see FIG. 2). Then, first, a search command is given to the servo circuit 23, and the light beam 3₁Is moved to the position of the track (x-6), and thereafter, the focus bias voltage generation circuit 22₄To control V_fAfter initialization to = 0V, a tracking servo ON command and a thread servo ON command are given to the servo circuit 23 to turn on the tracking servo and the thread servo. As a result, the light beam 3 emitted from the optical pickup 2A₁~ 3₅Focuses and tracks on tracks (x-6) to (x-2) (see I in FIG. 2). However, since the focus bias has not been adjusted yet, the light beam 3₁~ 3₅Are not in the optimum focusing state.
[0061]
Each light beam 3₁~ 3₅Is reflected by the signal surface 1A of the CD-ROM 1, the return light beam is a photodetector PD.₁~ PD₅Receives light and the photocurrent I₁~ I₅And the photo detector PD₁, PD₂, PD₄, PD₅Photocurrent I from₁, I₂, I₄, I₅Is the current / voltage converter 21₁, 21₂, 21₄, 21₅Current / voltage conversion by the RF signal RF₁, RF₂, RF₄, RF₅Is formed, and the waveform equalization circuit 24A₁, 24A₂, 24A₄, 24A₅The first signal processing circuit 26₁, 26₂, 26₄, 26₅Is entered. Also, photo detector PD₃Photocurrent I from₃-A to I₃-D is the current / voltage converter 21₃-A to 21₃The voltage value V_A~ V_DAnd the adder 22 of the arithmetic unit 22₁RF signal RF₃Is formed. Then, the waveform equalizing circuit 24A₃The first signal processing circuit 26₃Is entered.
[0062]
First signal processing circuit 26₁~ 26₅Are the input RF signals RF₁~ RF₅On the other hand, binarization, clock recovery using a PLL circuit, bit demodulation, frame synchronization detection, EFM demodulation, and subcode demodulation are performed, and the data after EFM demodulation (including P and Q parities) DATA₁~ DATA₅Is the A-time data AT of the subcode Q channel corresponding to one block unit.₁~ AT₅Output with First signal processing circuit 26₁~ 26₅Is the demodulated data DATA₁~ DATA₅Are serially output one symbol (8 bits) at a time. Also, the first signal processing circuit 26₁~ 26₅Detects a frame synchronization signal, and outputs an H level frame synchronization detection signal FS.₁~ FS₅And the first signal processing circuit 26₃Measures the amount of jitter of the binarized RF signal and outputs the jitter amount data JD₃Is output to the system controller 50. Also, the first signal processing circuit 26₃Is A-time data AT₃Is output to the system controller 50.
[0063]
The system controller 50 performs a search operation to transmit each light beam 3 of the optical pickup 2A.₁~ 3₅After on-tracking on tracks (x-6) to (x-2), a focus bias adjustment process is executed according to FIG.₃Data JD output from the₃Is the focus bias voltage V that minimizes_fIs the focus bias voltage generation circuit 22₄To cancel the offset due to the variation in the optical system and focus servo system of the optical pickup 2A,₃Is completely focused on the signal surface 1A (in FIG. 1, the light beam 3₃Focus point P₃Coincides with the signal surface 1A). At this time, another light beam 3₁, 3₂, 3₄, 3₅Is also in a state close to a perfect focus state with respect to the signal surface 1A (in FIG. 1, the light beam 3₁, 3₂, 3₄, 3₅Focus point P₁, P₂, P₄, P₅Comes near the signal plane 1A).
[0064]
Each light beam 3 at this time₁~ 3₅The waveform equalization circuit 24A is capable of compensating for high-frequency attenuation due to the spatial transmission frequency characteristic of₁~ 24A₅, And waveform equalization is performed with optimum characteristics. However, light beam 3₁And 3₅Have the same spatial transmission frequency characteristics, the waveform equalizing circuit 24A₁And 24A₅Waveform equalization with the same characteristics, and the light beam 3₂And 3₄Have the same spatial transmission frequency characteristics, the waveform equalizing circuit 24A₂And 24A₄As a result, waveform equalization is performed with the same characteristics.
[0065]
(2) Data reproduction operation (see FIG. 2)
When the focus bias adjustment is completed as described above, the first signal processing circuit 26₃Latest A-time data AT input from₃From the A-time data indicated by A and the A-time at the reproduction start point designated by the host computer,₁A track jump direction is determined by setting the track jump direction for turning on the track (x-1) on the inner circumference side of one track x including the A-time of the reproduction start point, and the number of tracks to be jumped.
If the optical pickup 2A is at the position II in FIG. 2 when the focus bias adjustment is completed, the optical pickup 2A is caused to make a track jump by four tracks in the forward direction, and the light beam 3₁~ 3₅On tracks (x-1) to (x + 3) (see III in FIG. 2), respectively, and the photodetector PD₁~ First signal processing circuit 26₁, Photodetector PD₂~ First signal processing circuit 26₂, Photodetector PD₃~ First signal processing circuit 26₃, Photodetector PD₄~ First signal processing circuit 26₄, Photodetector PD₅~ First signal processing circuit 26₅, The simultaneous reading of the recording data of the tracks (x-1) to (x + 3) is started, and the first signal processing circuits 26₁~ 26₅To H level frame synchronization detection signal FS₁~ FS₅Is input to the parallel / serial conversion unit 30.
[0066]
The parallel / serial conversion unit 30 that has received the write / read command outputs the first signal processing circuit 26₁~ 26₅Data output from₁~ DATA₅To the memory 32₁~ 32₅Write to. Then, the CD-ROM 1 is rotated by approximately one rotation (actually, slightly more than one rotation), and each light beam 3₁~ 3₅When there is no missing data in the data read by the system (see IV in FIG. 2), the memory 32₁~ 32₅To the memory 32 in the A-time order and without duplication or omission.₁~ 32₅, And outputs the read signal to the second signal processing circuit 40, and gives a track jump command to the system controller 50. Upon receiving the track jump command, the system controller 50 controls the servo circuit 23 to control each light beam 3 of the optical pickup 2A.₁~ 3₅Is caused to jump by three tracks in the forward direction, and the light beam 3₁~ 3₅Are focused and on-track on tracks (x + 3) to (x + 7) (see V in FIG. 2).
[0067]
Then, each first signal processing circuit 26₁~ 26₅To H level frame synchronization detection signal FS₁~ FS₅Is output to the parallel / serial conversion unit 30 at the point where is input. Upon receiving the track jump completion notification, the parallel / serial conversion unit 30 sets the first signal processing circuit 26₁~ 26₅Data after track jump output from₁~ DATA₅To the memory 32₁~ 32₅Write to. Then, the CD-ROM 1 makes almost one rotation (actually, one more rotation), and each light beam 3₁~ 3₅When there is no missing data in the data read by the system (see VI in FIG. 2), the memory 32₁~ 32₅To the A-time next to the A-time corresponding to the data last output to the second signal processing circuit 40 in the A-time order and without duplication or omission. Memory 32 as₁~ 32₅, And outputs the read signal to the second signal processing circuit 40, and gives a track jump command to the system controller 50.
[0068]
Upon receiving the track jump command, the system controller 50 controls the servo circuit 23 to control each light beam 3 of the optical pickup 2A.₁~ 3₅Is caused to jump by three tracks in the forward direction, and the light beam 3₁~ 3₅Is focused and on-tracked on tracks (x + 7) to (x + 11) (see VII in FIG. 2), and thereafter, the parallel / serial converter 30 and the system controller 50 repeat the same operation.
[0069]
The second signal processing circuit 40 receives the data serially output from the parallel / serial conversion unit 30, first descrambles one block at a time, and then performs error detection / correction based on the CIRC code (error detection / error based on P parity). Correction, deinterleaving, and error detection / correction by Q parity) to demodulate Lch data and Rch data conforming to the CD-DA standard. The CD-ROM data is demodulated by performing error detection / correction using rumble, header detection, EDC and ECC codes, and outputs the data to an external host computer.
[0070]
According to this embodiment, five light beams 3₁~ 3₅Of the pair, the light beam 3 of the + 1st-order diffracted light₄And -1st order diffracted light beam 3₂(A pair of +2 order diffracted light beams 3₅And second-order diffracted light beam 3₁) And the light beam 3 of the 0th-order diffracted light₃Is a light beam 3 of the 0th-order diffracted light which is formed completely axisymmetrically with respect to₃Irradiating the signal surface 1A of the CD-ROM 1 completely line-symmetrically with respect to the₄And 3₂(3₅And 3₁) Can hit the signal surface 1A of the CD-ROM 1 with the same beam cross-sectional area.₄And 3₂(3₅And 3₁) Can be the same. Therefore, the pair of light beams 3₄And 3₂(3₅And 3₁), A pair of waveform equalizing circuits 24A provided corresponding to₄And 24A₂(24A₅And 24A₁) Can set the same waveform equalization characteristics to each other, so that a total of five light beams 3₁~ 3₅, The waveform equalization characteristics need only be designed for three waveform equalization circuits.
[0071]
In the above-described embodiment, the light beam 3 which is the 0th-order diffracted light is adjusted by the focus bias adjustment.₃Is completely focused on the signal surface 1A. At this time, as shown in FIG.₃Focus point P₃Is the light beam 3 which coincides with the signal surface 1A but is ± 1st-order diffracted light.₂, 3₄Focus point P₂, P₄Is a position slightly deviated below the signal surface 1A, and is a light beam 3 which is ± 2nd-order diffracted light.₁, 3₅Focus point P₁, P₅Comes to a position slightly further below the signal surface 1A. Therefore, the light beam 3₁, 3₅When the CD-ROM 1 has a large surface runout, the light beam 3₁, 3₅It may not be possible to reproduce data in this system.
[0072]
As a measure against this, for example, as shown in FIG.₃Focus point P₃And light beam 3₁(3₅) Focus point P₁(P₅11) is set to L (see FIG. 3) as viewed in the optical axis direction of the objective lens 8 after the processing in step S13 or S18 or S23 in FIG.₄And V_fIs further changed by a certain fixed amount, and the objective lens 8 is moved in a direction away from the signal surface 1A by L / 2. Then, the light beam 3 when viewed in the optical axis direction of the objective lens 8₃Focus point P₃And light beam 3₁(3₅) Focus point P₁(P₅) Is exactly at the signal surface 1A of the CD-ROM 1 (see FIG. 3). In this manner, during the subsequent data reproduction, the objective lens 8 moves following the surface deflection of the CD-ROM 1 by the action of the focus servo system, so that the light beam 3 is transmitted regardless of the surface deflection of the CD-ROM 1.₁~ 3₅Can be maintained in a state close to a perfect focus state with respect to the signal surface 1A.₁~ 3₅Focus point P₁~ P₅Does not largely deviate from the signal surface 1A, and the light beam 3₁~ 3₅In any of the systems, the reading of data from the CD-ROM 1 can be executed reliably.
[0073]
At this time, the waveform equalizing circuit 24A₁~ 24A₅Is changed to a characteristic corresponding to the in-focus state in FIG. Even in the case of FIG.₄And 3₂(3₅And 3₁) Are the same, the pair of light beams 3₄And 3₂(3₅And 3₁), A pair of waveform equalizing circuits 24A provided corresponding to₄And 24A₂(24A₅And 24A₁) Can set the same waveform equalization characteristics.
[0074]
Also, the first signal processing circuit 26₁, 26₂, 26₄, 26₅The jitter amount of the binarized RF signal is also measured, and the jitter amount data JD₁, JD₂, JD₄, JD₅May be added, and the focus bias adjustment processing of FIG. 11 may be changed as shown in FIG.
In FIG. 4, the system controller 50 first_f= 0V, the first signal processing circuit 26₁~ 26₅Jitter data JD measured at₁~ JD₅Is read, and the average value is stored in a built-in memory (not shown) as jd (0) ′ (step S110). Next, the focus bias voltage generation circuit 22₄And V_fIs increased from 0 V by plus ΔV (ΔV is a positive value), and the jitter amount data JD at this time is increased.₁~ JD₅And the average value is stored in a built-in memory (not shown) as jd (+1) ′. Also, V_fIs reduced from 0 V to the minus side by ΔV, and the jitter amount data JD at this time is reduced.₁~ JD₅Is read, and the average value is stored in a built-in memory (not shown) as jd (-1) ′ (step S111).
[0075]
Then, the sizes of jd (+1) ', jd (0)', and jd (-1) 'are compared, and if jd (+1)'> jd (0) '<jd (-1)' (step YES at S112), V_fIs 0 V, the average jitter amount is the lowest, and similarly to FIG.₃Focus point P₃And light beam 3₁(3₅) Focus point P₁(P₅), The signal surface 1A of the CD-ROM 1 is almost at the center. At this time, the light beam 3₁~ 3₅Are in a state close to a perfect focus state with respect to the signal surface 1A, and there is no light beam greatly deviating from the perfect focus state.₄And V_fIs set to 0 V, and the adjustment is completed (step S113).
[0076]
If jd (+1) '> jd (0)' <jd (-1) 'instead of jd (+1)' <jd (0) '<jd (-1)' (YES in step S114), k = 2 (step S115), and V_f= (+ 2) · ΔV, and the jitter amount data JD at this time₁~ JD₅Is read and the average value is set to jd (+2) ′ (step S116). If jd (+2) '> jd (+1)' <jd (0) '(YES in step S117), V_fIs (+1) · ΔV, the average jitter amount is the lowest, and the light beam 3₃Focus point P₃And light beam 3₁(3₅) Focus point P₁(P₅), It is considered that the signal surface 1A of the CD-ROM 1 has come almost in the middle.₄And V_fIs set to (+1) · ΔV, and the adjustment is finished (step S118).
[0077]
If jd (+2) '> jd (+1)' <jd (0) '(NO in step S117), k is incremented to 3 (step S119), and the process returns to step S116 to repeat the same processing. If jd (+ k) ′> jd ｛+ (k−1)｝ ″ <jd ｛+ (k−2)｝ ′ at a certain value of k (YES in step S117), V_fIs {+ (k−1)} · ΔV, the average jitter amount is the lowest, and when viewed in the optical axis direction of the objective lens 8, the light beam 3₃Focus point P₃And light beam 3₁(3₅) Focus point P₁(P₅), It is considered that the signal surface 1A of the CD-ROM 1 has come almost in the middle.₄And V_fIs set to {+ (k−1)} · ΔV, and the adjustment is completed (step S118).
[0078]
If jd (+1) ′ <jd (0) ′ <jd (−1) ′ in step S114, k = 2 (step S120), and V_f= (− 2) · ΔV, and the jitter amount data JD at this time₁~ JD₅Is read and the average value is set to jd (−2) ′ (step S121). If jd (−2) ′> jd (−1) ′ <jd (0) ′ (YES in step S122), V_fIs equal to (−1) · ΔV, the average amount of jitter is the lowest, and when viewed in the optical axis direction of the objective lens 8, the light beam 3₃Focus point P₃And light beam 3₁(3₅) Focus point P₁(P₅), It is considered that the signal surface 1A of the CD-ROM 1 has come almost in the middle.₄And V_fIs set to (−1) · ΔV, and the adjustment is completed (step S123).
[0079]
If jd (−2) ′> jd (−1) ′ <jd (0) ′ in step S122, k is incremented to 3 (step S124), and the process returns to step S121 to repeat the same processing. If jd ｛− (k−2)｝ ″> jd ｛− (k−1)｝ “<jd (−k) ′ (YES in step S122), V_fIs equal to {− (k−1)} · ΔV, the average jitter amount is the lowest, and the light beam 3 when viewed in the optical axis direction of the objective lens 8₃Focus point P₃And light beam 3₁(3₅) Focus point P₁(P₅), It is considered that the signal surface 1A of the CD-ROM 1 has come almost in the middle.₄And V_fIs set to {− (k−1)} · ΔV, and the adjustment is completed (step S123).
[0080]
When the focus bias adjustment is completed in this manner, the light beam 3₁~ 3₅Can be brought into a state close to a perfect focus state with respect to the signal surface 1A.₁~ 3₅Focus state can be easily optimized. The focused state at this time is almost the same as that in FIG. During the subsequent data reproduction, the objective lens 8 moves following the surface deflection of the CD-ROM 1 by the function of the focus servo system.₁~ 3₅Can be maintained in the optimum focus state with respect to the signal surface 1A, and the light beam 3₁~ 3₅Focus point P₁~ P₅Does not largely deviate from the signal surface 1A, and the light beam 3₁~ 3₅In any of the systems, data can be read from the CD-ROM 1 more reliably.
[0081]
When changing the processing of FIG. 11 to the processing of FIG.₁~ 24A₅Is changed to a characteristic corresponding to the in-focus state in FIG. A pair of light beams 3₄And 3₂(3₅And 3₁) Are the same, the pair of light beams 3₄And 3₂(3₅And 3₁), A pair of waveform equalizing circuits 24A provided corresponding to₄And 24A₂(24A₅And 24A₁) Can set the same waveform equalization characteristics.
[0082]
Also, in the processing of FIGS. 11 and 4 described above, the first signal processing circuit 26₃(26₁~ 26₅) Jitter amount data JD measured in)₃(JD₁~ JD₅) Using JD₃Value (JD₁~ JD₅Voltage value V at which the average value of_fIs set to adjust the focus bias, but in contrast to this, for example, the first signal processing circuit 26₃(26₁~ 26₅), After descrambling the EFM demodulated data in units of one block, error detection / correction based on the CIRC code (error detection / correction using P parity, deinterleaving, error detection / correction using Q parity) is performed. The error rate detected by the error detection by the P parity at the time is measured, and the error rate data ED₃(ED₁~ ED₅) Is added. 11 and FIG.₃(JD₁~ JD₅) Is ED₃(ED₁~ ED₅) And ED₃Value (ED₁~ ED₅The bias voltage value V at which the average error rate, which is the average value of_fIs set by adjusting the focus bias, the light beam 3 can be adjusted as shown in FIG. 1 (FIG. 3).₁~ 3₅Focus point P₁~ P₅In the vicinity of the signal surface 1A, and the light beam 3₁~ 3₅Can be brought into a state close to an almost perfectly focused state with respect to the signal surface 1A.
[0083]
The measurement of the error rate for each system may be performed using the second signal processing circuit 40. That is, when the second signal processing circuit 40 performs error detection / correction based on the CIRC code (error detection / correction using P parity, deinterleaving, error detection / correction using Q parity), the error is detected by P parity. An error rate detection circuit that measures the error rate and outputs error rate data is added. When adjusting the focus bias, the first signal processing circuit 26₃(26₁~ 26₅) Output data DATA₃(Data DATA₁~ DATA₅) Are sequentially input to the second signal processing circuit 40 for each system via the parallel / serial conversion unit 30, and the error rate is measured for each system by the second signal processing circuit 40.₃Error rate data ED of the system₃(Light beam 3₁~ 3₅Error rate data ED for each system₁~ ED₅) Is output and ED₃Value (ED₁~ ED₅Voltage value V at which the average value of_fTo be set.
[0084]
In the processing of FIG. 11 and its modification, all five light beams 3₁~ 3₅Bias voltage value V so that the average value of jitter amount (average error rate) of the_fWas set, but five light beams 3₁~ 3₅Of which, light beam 3₁And 3₃Or two beams, or light beam 3₂And 3₄Two systems, or light beam 3₁And 3₃And 3₅The jitter amount of the binary RF signal or the error rate of the read data is measured for each of the predetermined two or more light beam systems out of n = 5 light beams such as the three systems described above, and the measured jitter is measured. The focus bias may be adjusted so that the average value of the amount or the error rate is minimized. In this case, the light beam having a poor focus state with respect to the signal surface 1A regardless of the surface deflection of the CD-ROM 1. Can be avoided, and data can be reliably read from the CD-ROM 1. Further, instead of measuring the error rate of the data symbol read from the CD-ROM 1, the sub-code of the sub-code read from the CD-ROM 1 is divided into two or more predetermined light beams out of n = 5 light beams. The error rate may be measured, and the focus bias may be adjusted so that the average value of the measured error rates is minimized.
[0085]
In the above-described embodiment, the CD-ROM is rotated at a constant linear velocity, but may be rotated at a constant angular velocity (CAV). Further, an optical disk having a track formed in a spiral shape of a type other than the CD-ROM, such as a CD-WO, a DVD, a DVD-ROM, a DVD-RAM, or a track formed concentrically may be used. Optical disks such as LDs and MOs may be used. Further, the number of light beams for simultaneously reading the recording data for each track may be a number other than 5, such as 3, 7, or the like.
[0086]
【The invention's effect】
According to the present invention, out of the (2m + 1) light beams, a pair of the + i-order diffracted light beam and the −i-order diffracted light beam (i = 1, 2,..., M) are set to 0. Formed completely line-symmetric with respect to the light beam of the order diffracted light, and completely line-symmetric with respect to the signal surface of the optical disc, with the light beam of the 0th-order diffracted light radiated perpendicularly to the signal surface. Therefore, the pair of light beams can have the same beam cross-sectional area when they hit the signal surface of the optical disk, and the spatial transmission frequency characteristics of the pair of light beams can be the same. Therefore, the pair of waveform equalizers provided corresponding to the pair of light beams can set the same waveform equalization characteristics to each other, so that when there are a total of (2m + 1) light beams, (m + 1) It is sufficient to design the waveform equalization characteristics only for the individual waveform equalization means.
[0087]
In addition, the optical system including the objective lens allows the signal surface of the optical disk to be positioned between the in-focus position of the 0th-order diffracted light beam and the in-focus position of the ± mth-order diffracted light beam when viewed in the optical axis direction of the objective lens. By arriving at the location, a light beam with a poorly focused state on the signal surface cannot be formed, so that data can be reliably read from the optical disc.
[Brief description of the drawings]
FIG. 1 is a block diagram of a multi-beam type CD-ROM reproducing device according to one embodiment of the present invention.
FIG. 2 is an explanatory diagram showing a reproducing operation of FIG. 1;
FIG. 3 is an explanatory diagram of a focused state of a light beam according to a modification of FIG. 1;
FIG. 4 is a flowchart illustrating a focus bias adjustment process according to a modification of FIG. 1;
FIG. 5 is a block diagram of a conventional multi-beam type CD-ROM reproducing device.
FIG. 6 is a specific configuration diagram of a calculation unit in FIG. 5;
FIG. 7 is a specific configuration diagram of a parallel / serial conversion unit in FIG. 5;
FIG. 8 is an explanatory diagram showing an example of contents stored in a memory in FIG. 5;
FIG. 9 is an explanatory diagram showing an example of the reproducing operation of FIG. 5;
FIG. 10 is an explanatory diagram showing an example of contents stored in a memory in FIG. 5;
FIG. 11 is a flowchart showing focus bias adjustment processing by a system controller in FIG. 5;
[Explanation of symbols]
1 CD-ROM 1A signal surface
2A Optical pickup 3 Laser beam
4 Laser diode 5 Grating
6 Beam splitter 7 Collimator lens
8 Objective lens 9 Focus actuator
10 Tracking actuator 11 Thread motor
20A Recorded data reproduction system
21₁, 21₂, 21₃-A, 21₃-B, 21₃-C, 21₃-D, 21₄, 21₅  Current / voltage converter
22 arithmetic unit 22₁, 22₅  Adder
22₂, 22₃  Adder / subtractor
22₄  Focus bias voltage generation circuit
23 Servo circuit 24A₁~ 24A₅  Waveform equalization circuit
26₁~ 26₅  First signal processing circuit 30 Parallel / serial converter
40 second signal processing circuit 50 system controller

Claims (3)

Different n light beams are simultaneously irradiated on n different tracks (where n is an odd number of 3 or more) having different signal surfaces of the optical disk, and an RF signal is formed for each light beam from a detection output obtained by separately detecting each return beam. Then, the RF signal of each light beam is subjected to high-frequency compensation for increasing the high-frequency gain by performing waveform equalization by individually provided waveform equalizing means, and then binarizing each RF signal by the signal processing means. In a multi-beam type optical disc reproducing apparatus which reads demodulated and recorded data recorded on a track irradiated with each light beam,
One laser beam generated by the laser beam generating means is vertically incident on the diffraction grating, and the 0th-order diffracted light, ± 1st-order diffracted light,... ± mth-order diffracted light (where m is (n−1) / 2) ) To form (2m + 1) light beams,
The (2m + 1) light beams are focused near the signal surface of the optical disk by an optical system including an objective lens. At this time, the optical system is arranged so that the optical beam of the 0th-order diffracted light is irradiated on the optical disk vertically. And
Among the waveform equalizers, a pair of waveform equalizers provided corresponding to the + i-order diffracted light beam and the −i-order diffracted light beam (where i is 1, 2,..., M) Set the same waveform equalization characteristics to each other ,
When viewed in the optical axis direction of the objective lens, the signal surface of the optical disk is located at a predetermined position between the focusing position of the 0th-order diffracted light beam and the focusing position of the ± mth-order diffracted light beam,
A multi-beam type optical disc reproducing apparatus characterized by the following. Different n light beams are simultaneously irradiated on n different tracks (where n is an odd number of 3 or more) having different signal surfaces of the optical disk, and an RF signal is formed for each light beam from a detection output obtained by separately detecting each return beam. Then, the RF signal of each light beam is subjected to high-frequency compensation for increasing the high-frequency gain by performing waveform equalization by individually provided waveform equalizing means, and then binarizing each RF signal by the signal processing means. In a multi-beam type optical disc reproducing apparatus which reads demodulated and recorded data recorded on a track irradiated with each light beam,
One laser beam generated by the laser beam generating means is vertically incident on the diffraction grating, and the 0th-order diffracted light, ± 1st-order diffracted light,... ± mth-order diffracted light (where m is (n−1) / 2) ) To form (2m + 1) light beams,
The (2m + 1) light beams are focused near the signal surface of the optical disk by an optical system including an objective lens. At this time, the optical system is arranged so that the optical beam of the 0th-order diffracted light is irradiated on the optical disk vertically. And
A focus servo means for moving the objective lens following the surface deflection of the optical disk and always focusing (2m + 1) light beams near the signal surface of the optical disk;
Among the waveform equalizers, a pair of waveform equalizers provided corresponding to the + i-order diffracted light beam and the −i-order diffracted light beam (where i is 1, 2,..., M) Set the same waveform equalization characteristics to each other ,
The focus servo means, when viewed in the optical axis direction of the objective lens, places the signal surface of the optical disc at a predetermined position between the focus position of the 0th-order diffracted light beam and the focus position of the ± mth-order diffracted light beam. To adjust the focus bias
Multi-beam optical disk reproducing apparatus according to claim. measuring means for measuring a jitter amount or an error rate of the binarized RF signal for each of two or more predetermined light beams of the n light beams;
The focus servo means, the focus bias adjustment so that the average value of the jitter amount or error rate measured by the measurement means is minimized,
3. The multi-beam type optical disk reproducing apparatus according to claim 2, wherein:

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