JPS61216183A - Information retrieving device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an information retrieval device that records information signals on a recording medium at high density and reads and reproduces desired information at high speed.

In particular, the present invention relates to a device that optically searches desired information at high speed from an optical disk in which information signals are recorded concentrically or spirally at high density on a rotating disk.

[Background of the invention]

Conventionally, as this type of search device, for example, Japanese Patent Laid-Open No. 54
There is a device disclosed in Japanese Patent No. 36906. In other words, the rough positioning of the optical head is performed using an external scale, and the positioning of the minute light spot with respect to the information track is performed by detecting the address signal written on the information track and using a deflection means such as a mirror to position the light spot. This is done by moving the . At this time, the scale pitch of the external scale is set to an integral multiple of the information track pitch to shorten the search time.

In this type of device, the speed of approaching the target block using the output of the linear scale is usually controlled in order to shorten the access time. In order to perform this speed control, a means for detecting the speed is required. Another detector (e.g. tachometer, etc.) to detect speed
If the head is removed, the weight of the head increases, and depending on the length of the tachometer sensor, it may cause vibration at a low frequency, and the price also increases. Therefore, it is preferable to detect the speed using a linear scale. That is, since the pulse frequency of the zero-cross detection signal is proportional to the moving speed of the head, the zero-cross detection signal can be frequency-voltage converted to detect the speed in the form of voltage. However, the frequency
Voltage conversion no longer shows an accurate value when the frequency is low (the moving speed of the head is slow). The reason for this is that the pulse interval of the zero cross detection signal becomes wider, making it impossible to detect speed fluctuations during this interval. Therefore, when speed control is performed using the output of the frequency/voltage conversion, when the target block is approached and the speed slows down, the control becomes unstable and may run out of control.

Furthermore, since macroscopic positioning is performed using an external scale that is unrelated to track eccentricity, the eccentricity increases microscopic movement and increases access time.

[Purpose of the invention]

An object of the present invention is to roughly position an optical head on a desired track of an optical disk using a coarse scale.
An object of the present invention is to provide an information retrieval device having speed detection means for stably performing speed control and optical head control means for shortening access time.

[Summary of the invention]

In order to solve the above-mentioned problems, in the present invention, when the moving speed of the optical head is slow, by using a track pitch that is sufficiently thinner than the external scale pitch as a scale, the speed of the optical head can be increased. Accurately detects speeds from low to low. Furthermore, the access time is shortened by detecting the track eccentricity state in advance and correcting the macro seek movement distance based on the eccentricity state.

[Embodiments of the invention]

FIG. 1 is a block diagram showing one embodiment of the present invention.

The disk 103 rotates around a rotation axis 1.04, and a guide track (
(not shown) is provided.

The light beam emitted from the semiconductor laser 300 is sent to the beam splitter 4
．． O011-/4 The number of wavelengths is 401, and a light spot 32 is formed on the disk surface -J2 by an objective lens 403 via a deflector 308. The reflected light beam from the disk 1o3 passes through an objective lens 403 and a deflector 308, has an optical path bent by a beam splitter 400, and is guided onto a photodetector 307. The photodetector 3(') 7 is based on the principle of detecting a rack deviation on a two-split detector as shown in FIG. 2, and the distribution pattern 411 on the two-split detector changes due to track deviation. Therefore, the difference between the outputs of the detectors 404 and 405 is calculated by the differential amplifier 40.
6 to obtain a track deviation detection signal 407.

The optical system described above is incorporated into the optical head 12, attached to the voice coil 68, and moved in the radial direction of the disk.

The optical head 12 includes an external scale 45 and a position sensor 4.
8 is included. In this embodiment, an optical linear scale using parallel slits will be explained as the external scale, but the external scale may be one using magnetism or other scales.

FIG. 3 shows a schematic diagram of an optical linear scale using parallel slits. Above the scale 45 is a shading pattern with a pitch p as shown in (a).

Here, hatched areas 40, 40' and 40' are opaque areas, and 41, 41' and 41' are transparent areas. On top of this scale 45, as shown in (b), a grating 46 having the same shading pattern as the scale 45 is superimposed as shown in (c), and irradiated with a light emitting diode 44 from the back side.
The transmitted light is received by a photodetector 47. Since this principle is already known, it will not be described in detail, but the photodetector 47, the grating 4
6. When the position sensor 48 integrated with the light emitting diode 44 is moved in the radial direction of the disk along the linear scale 45 in conjunction with the optical head 2, the output 33 of the photodetector 47 becomes as shown in FIG. 4(a). It changes like this. This signal 33
is input to the zero cross detection circuit 72 (FIG. 1), which generates a pitch detection signal 80 (FIG. 4(b)).

In the zero cross detection circuit 72, the difference between the signal 33 and the DC component e is detected by the differential amplifier 71 to obtain the signal 33'.
pulse 34' for the zero points 34, 35, 36, 37° 38.39 of the signal 33', respectively, by cutting ' at the zero level.

35', 36', 37', 38', and 39', and outputs a signal 8o as shown in FIG. 4(b).

As a first means of searching for a desired track, first,
- The address written on the rack must be detected and compared with the address of the desired track to determine the amount and direction of movement of the optical head.

The amount of movement of the optical head is represented by the number N of pulses of the pitch detection signal. If the address of the track where the light spot is currently located is address X, the address of the desired track is address Y, the track pitch is 4 μm, and the external scale pitch is 9 μm, then N = ((X-Y)X-]...
(1) becomes. Here, 0 indicates a Gaussian symbol.

The 274 tracks are grouped together into one block.

Then, the detection signal from the linear scale becomes a signal indicating the block. When searching, the controller 203 specifies the number of the block containing the desired track, and calculates the difference from the current block number. The signal 57 of the difference N between the block numbers is input to the comparison counter 81, and the output of this counter 8 is used as the RO to create the target speed curve.
M (Read Only Memory) 205, and this output is input to the D/A converter 207 to generate a target speed signal.

On the other hand, to detect the moving speed, the zero cross pulse signal 80 from the linear scale is sent to a frequency/voltage converter (F/V converter).
204 to detect a speed signal 226. Further, the track deviation signal 4.07 is passed through the F/■ converter 220 to detect the speed signal 227.

The access controller 203 starts the access operation, and provides a polarity switching circuit 209 with a polarity signal 56 that determines the radial direction of movement of the linear motor 68. Then, the linear motor 68 starts moving at maximum acceleration. Then, the speed signals 226 and 227 become as shown in FIG. 5(e) and (c). That is, the signal 226 has large ripples in the slow speed range and does not indicate the correct speed, but the signal 227 shows accurate speed even in the slow speed range. However, as the speed increases, the signal 227 no longer shows a correct value due to the limit of the detection frequency characteristics of the track deviation signal 407.

Therefore, the speed signal of signal 226 becomes stable and the speed signal of signal 226 becomes stable.
7, the speed signal is switched at the respective value E, ,E, at the travel speed where the speed signal still has the correct value. That is, the signal 226 is input to the speed determination circuit 410, and compared with the level E1, signals A and τ having different polarities are generated, and the switches 223 and 224 are controlled respectively. That is, when the signal 226 is lower than E, the signal 227 is passed through the amplifier 222 and sent to the adder 225 by the switch 224.
and when signal 226 is greater than E, signal 2
26 is supplied to an adder 225 via an amplifier 221 and a switch 223. The amplification factors of the amplifiers 221 and 222 are set to values such that equal outputs can be obtained for inputs at levels E and E2. In this way, the adder 22
The output of 5 becomes the synthesized speed signal 228, which is shown in Fig. 5 (
A desirable speed detection signal as shown in a) is obtained.

This speed detection signal 228 is compared with a target speed signal at differential amplifier 208. When the moving speed reaches the target speed, it enters constant speed mode, and at a certain point it enters deceleration operation, and the signal 226 is level E again, and when it becomes lower, the speed detection signal switches to signal 227, and this speed signal stabilizes the speed. Speed control is performed. When the value of the counter 81 reaches 1, a set pulse C is generated, which causes the flip-flop 214 to operate and generate a control signal B for switching the gate circuit 73 from the speed control signal to the positioning control signal.

In this embodiment, a case has been described in which the optical head is positioned at a desired position on a linear scale, but the present invention is also applicable to positioning on a track as described in Japanese Patent Application Laid-open No. 58-91536, which was previously proposed by the present applicant. It can also be applied in cases. That is, the control signal B causes the deflector 308 to
The near motor 68 is driven in conjunction with the near motor 68 to start the pull-in operation to the near track. Regarding the speed signal 227, the speed signal 227 is disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 58-91536.
It will be more stable if the passing direction and number of trucks are detected using the signals 407 and 412 in FIG. 2, and the polarity of the speed signal is also determined. Here, the signal 412 is a signal obtained by adding the outputs of the photodetectors 404 and 405 by an adder 413.

Furthermore, another embodiment of the present invention will be described with reference to FIG. 6.8. The method of macroscopically positioning the light spot near the target track using an external scale, then pulling it into the track once, reading out the address, finding the difference from target 1 to Rack, and moving microscopically for each track is not possible. The amount of movement varies depending on the state of track eccentricity, lengthening the overall access time. Therefore, by detecting the influence of eccentricity in advance, the amount of microscopic movement can be reduced and the access time can be shortened.

The device of the present invention uses an external scale to position the optical head at the innermost position in the radial direction of the disk when the device is started or when a disk is loaded, and when the disk rotation becomes steady, the light spot is placed on a white spot on the disk surface. After matching,
The device is in use. If there is eccentricity at this time, as the disk rotates, each time the track passes over the optical spot, the phase relationship between the track deviation signal 407 and the signal 412 representing the total amount of light that has passed from the disk through the objective lens changes. Change. These two signals 407.412
can be used to detect eccentricity. That is, as shown in FIG. 6, signals 407 and 412 are input to the direction discrimination circuit 430, and each time a track passes, a pulse corresponding to the passing direction (for example, a pulse signal 431 is generated when the disk passes from the inner circumference to the outer circumference). And vice versa, the signal (]
2) Generate 432), input signals 411 and 432 to the up direction (TJ) and down direction (D) inputs of the up/down counter 433, respectively, and
The activation of 33 corresponds to one position in the circumferential direction of the disk, and uses a pulse signal 434 generated every time the disk rotates. In this way, the unit of the output of the counter 433 is track pitch. Therefore, it is input to the bit conversion circuit 435 so that it is in units of linear scale pitch. This data is written into RAM (Random Access Memory) 436. At this time, data t from the current time generation circuit 437, which generates data corresponding to the time measured from the pulse signal 434, is used as the designated address of the RAM.

In this way, as shown in FIG. 8(a), the RAM4
-36 memory space stores the state of the disk eccentricity over time, with the address as time and the recorded data as the eccentricity amount.

Next, a method for reducing the amount of microscopic movement will be described. By calculating the time used for macro seek in advance, the amount of movement of the target track can be predicted from the detected eccentricity state described above, and by correcting the number of macro seeks from this amount, the eccentricity of the target track can be almost reached by macro seek. can be approximated without any error.

A configuration for implementing this method is shown in FIG. The access controller 203 issues a command for the amount of movement S to the target track in units of external scale pitch, and stores the amount of movement S in the ROM (Read Only Memory) 438
Enter the address. In the memory space of the ROM 438, macro seek characteristics are stored, as shown in FIG. 8(b), in which the address is the moving distance of the optical head and the recording data is the moving time. This characteristic includes all the times used for macro seek, such as acceleration, deceleration, and settling time.

If you specify the travel distance, this time can be determined by using an external scale, which is an absolute scale that can be stably detected, for control, so there are few fluctuations in the characteristics of the macro seek mechanism system, so there are few errors, and the travel time can be determined with good reproducibility. characteristics are obtained. Therefore, once the detector and exhaust system are determined, this characteristic curve can be uniquely determined and stored in the ROM 4-38.

If there is a change in the characteristics, use R instead of ROM43B.
Using A and M, the time characteristics of the macro seek may be measured and corrected from time to time.

When such a ROM 4.38 is used, when the moving amount S is entered in the address, the moving time t is output correspondingly. Start macro seek from the current time ta to find the movement amount of the target track after the movement time tl.
, and 1. data is added to an adder 439, the output thereof is input to a divider 44.0, the division is performed by data corresponding to the rotation period T of the disk, and the remainder t is output. When this tl is input to the read address of the RAM 436, as shown in FIG. 8(a), the movement amount of the target track after the movement time tl, that is, the correction value As of the macro seek movement amount is determined. This As is input to the adder 441 together with S, and its output is used as the movement amount of the macro seek for the first
It is used for the signal 57 input to the counter 81 in the figure.

Furthermore, another embodiment will be described using FIGS. 7 and 8. If the eccentricity is large or the rotational speed is high, even if the object is positioned near the target track by macro seek as in the above-described embodiment, it may not be possible to pull the object into the track.

Therefore, when the macro seek movement is completed, the eccentric speed of the track is at its minimum (times 1, , and t, in Fig. 8(a)). Adjust startup timing. A configuration for realizing this is shown in FIG. The output from the bit converter 435 indicating the eccentric state is input to the maximum/minimum value detection circuit 442, and the timing is determined based on the current time t. Maximum minimum detection circuit 4
42 is a well-known circuit that has a memory that retains the previous state, compares the contents of the memory with sequentially input data, and replaces the contents of the memory depending on whether the data is larger or smaller. By this detection circuit 442, as shown in FIG.
Maximum value X, 1. is the memory 445, time t indicating the maximum value, , is the memory 446, minimum value X+al is the memory 443, time t indicating the minimum value, 1. is entered into memory 444.

When the macro seek movement amount S is specified, the movement time t,
is determined in the same manner as in the previous embodiment, and the current time 1. The remaining time t4 is obtained by calculating the following. This t, and t'
lam, t, . . . are input to the determination circuit 448, and depending on the number of people, a signal 45 is generated that specifies the waiting time 7jt from the current time to start macro seek and the moving leaf sound to be corrected.
Generates 1.

That is, 1. ,, When (1,i, , tact, ,
, then At is tllall -t, s is Xl,
.

tllall <td<'r, t, then At is t,
,, -t,, S is X11, if tl>t-+- then 71t is T+t-,, -t,, S is xl, a data switching circuit whose output of 1 is controlled by the judgment circuit 448 and signal 451 447. Such a determination circuit 448 can also be realized by a general-purpose microcomputer.

At is loaded into a counter 449 and counted down by a clock 453 of a constant period, and when it reaches zero, a timing signal 452 for starting macro seek is generated. This signal may be used, for example, as a load signal for the counter 81 in FIG. Further, the signal S is input to the adder 450 along with S, and the output thereof is used as the input signal 57 of the counter 81.

According to this embodiment, track pull-in after macro seek can be performed stably and in a short access time.

Although the embodiments described above have been described as hardware configurations for explaining the circuit configurations, they can also be implemented using a microcomputer or the like.

〔Effect of the invention〕

According to the present invention, even in an access method using an external scale, speed control can be performed stably and the access time can be shortened without being affected by eccentricity.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a practical example of the present invention 4911, Fig. 2 is a block diagram showing an example of a detector used in the embodiment of Fig. 1, and Fig. 3 is an example of an external scale and its detector. FIG. 4 is a waveform diagram thereof, FIG. 5 is a waveform diagram for explaining the present invention in detail, FIG. 6 is a block diagram showing main parts of another embodiment of the present invention, and FIG. 8 is a block diagram showing the main part of another embodiment of the present invention, and FIG. 8 is an explanatory diagram of the memory space of the memory used in the present invention.・Pa. Agent Patent attorney Katsuma Ogawa ゛・ 〉 Dai $u@J

Claims (1)

[Claims] 1. An optical disc search device using an external scale, characterized in that a stable speed detection signal is obtained by selecting speed signals based on the external scale and track scale according to the moving speed. Information retrieval device. 2. The information retrieval device according to item 1, characterized in that the access time is shortened by detecting the state of track eccentricity in advance and correcting the movement amount of macro seek. 3. The information retrieval device according to item 2, wherein the start timing of the macro seek is adjusted so that the eccentric speed is minimized during track pull-in after the macro seek.