JPS60201536A - Tracking control system - Google Patents

Abstract

PURPOSE:To guide a recording beam spot at a nearly constant track pitch on an optical recording medium without any tracking track in advance by deciding the width of a tracking beam spot to a value or over being a subtraction of an information track width from a distance two times the prescribed interval. CONSTITUTION:An optical beam is irradiated with a recording power from a light source 1 and a tracking optical beam is irradiated from a light source 2, and each beam is condensed on the optical recording medium. The information is recorded (recording pit 20) by a beam spot 12 at recording, and a tracking error signal P and a reflection light total amount signal O are obtained with the similar operation at reproduction by the reflecting light from the tracking beam spot 13. The tracking beam spot 13 at recording is formed so as to be in contact with the innermost circumferential track of an information track 19 recorded already. The spot width of the tracking beam spot 13 is (2X track pitch) - (information track width).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a tracking control method for controlling the position of a recording beam spot on an optical recording medium that does not have a tracking track such as a pregroove.

There is an increasing need to convert information into electrical signals, store large amounts of information, and quickly retrieve only the required information when needed.In recent years, optical information recording and reproducing devices have been developed to meet these demands. It has been in the spotlight, spurring technological development. The optical information recording and reproducing device is.

It has various advantages over conventional magnetic disk drives. For example, since information can be written and read without contact using light, there is no need to worry about dust on the optical recording medium or the head, and there is almost no impact from dust, which is a big problem when increasing density. The most advantageous points are 5
Since it is possible to utilize optical detection servo technology,
This makes it possible to extremely increase recording density. Compared to magnetic disk drives that rely solely on mechanical precision, it is possible to record at a density several tens of times higher.

By the way, in order to perform high-density recording using such an optical information recording/reproducing device, a tracking track is formed in advance on the optical recording medium to be used, and during recording, information is recorded while tracking the tracking track. This tracking track is generally formed as a groove on an optical recording medium by a stamping method used in the production of so-called video discs. However.

This video disc manufacturing process begins with the need for a precision master creation machine, and a series of steps such as photoresist coating, etching, electroforming, and stamping must be performed in a dust-free environment, and the VLSI manufacturing Similar to the process, it requires expensive capital investment and a lot of manpower. For this reason, manufacturing costs have increased, making optical recording media expensive.

It also has a protective film. Dust that adheres to a completed optical recording medium has little effect on recording, but
Dust that adheres during the production of optical recording media can be as small as 1 meter in diameter.
Even the size of μ can cause bit loss. In other words, the more optical recording medium manufacturing processes there are, the higher the probability that this dust will adhere, and the simpler the i-manufacturing process is, the more advantageous it will be in terms of error rate.

In this way, from the viewpoint of manufacturing cost and error rate, the optical recording medium manufacturing process is simple and good, and ideally it is possible to produce high-density optical recording media on a smooth optical recording medium without tracking tracks. is to record information.

However, when recording information on an optical recording medium that does not have a tracking track, deviations in the center of one rotation are caused, and new information is recorded on the outer (or inner) information track and the inside (or outside) of it. Recorded information tracks may overlap, and to prevent such overlap, a sufficient track pitch must be set, which reduces the recording density and reduces the information capacity of a single optical recording medium. There were some problems.

The object of the present invention is to solve the above-mentioned problems.

To provide a tracking control method that can guide a recording beam spot at a substantially constant track pitch on an optical recording medium that does not have a tracking track in advance, and can facilitate the formation of a tracking beam spot. That's true.

In order to achieve this object, the present invention forms a tracking beam spot at a position a predetermined distance ahead of the recording beam spot in the recording direction, and changes the width of the tracking beam from twice the fixed interval to It is characterized by setting the width of the information track to be equal to or greater than the value obtained by subtracting the information track width, so that the area where the recording beam spot is scheduled to be irradiated and the area at the interval from the information track are pre-scanned by the tracking beam spot. shall be.

The present invention will be explained in detail below with reference to FIGS. 1 to 5.

FIG. 1 is a diagram schematically showing an optical information recording/reproducing apparatus for implementing the present invention. 1 is a recording/reproducing light source, 2 is a tracking light source, 3.4 is a collimator lens, 5 is /
6 is a dichroic mirror, 7 is a tracking mirror, 8 is an objective lens that focuses the light beam emitted from the light source 1.2 onto the optical recording medium 9 as a minute spot, 10 is a condenser lens, 11 is an A photodetector that receives reflected light from the optical recording medium 9, and includes a light receiving section 11a that receives reflected light from a recording/reproducing beam spot and a light receiving section 11b that receives reflected light from a tracking beam spot. There is.

FIG. 2 is a diagram showing the positional relationship and shape of the recording/reproducing beam spot and the tracking beam spot. Reference numeral 12 denotes a beam spot 1 for recording and reproducing that is emitted from the light source 1 and focused onto the optical recording medium 9 by the objective lens 8.
3 is a tracking beam spot emitted from the light source 2 and focused on the optical recording medium 9 by the objective lens 8; the spot diameter of the tracking beam spot 13 is larger than the spot diameter of the recording/reproducing beam spot 12; is also large, and its shape is not limited to a circle, but also an ellipse (Fig. 2, 13a)
) and other shapes are also acceptable. Each beam spot 12, 13 is located on the same scanning line with respect to the recording direction (arrow in FIG. 2), and the distance between them is always constant.

FIG. 3 is a block diagram showing part of the tracking control circuit. P is a tracking error signal obtained by reflected light from the tracking beam spot 13, 0 is a reflected light total amount signal which is the total amount of reflected light from the tracking beam spot 13, and 14 is a reflected light total amount signal 0 is a predetermined value (described later). ) A comparator that determines whether the reflected light total amount signal O is higher than a predetermined value outputs a high-level signal. 15 is a constant voltage circuit, 16 is a switch circuit 1. Normally, the contact a side (the state shown in Figure 3) is closed.
When a high level signal is input from the comparator 14, the contact is switched from the contact a side to the contact side. A drive circuit 17 drives the tracking mirror 7 (in the direction of the arrow in FIG. 1) via a tracking coil 18.

FIG. 4(a) is a diagram showing the positional relationship between the information track and each beam spot, where 19 is an information track where information has already been recorded, and 20 is a recording pit where information is being recorded. FIG. 4(b) is a diagram showing the tracking error signal P with respect to a change in the radial position of the tracking beam spot 13 on the optical recording medium 9, and FIG. FIG. 3 is a diagram showing a reflected light total amount signal 0, which is the total amount.

FIG. 5 is a schematic diagram showing the relationship between the tracking beam spot image 13' projected onto the light receiving section 11b and the information track image 19'. Signal P is zero. (11)
indicates a state in which a tracking error occurs in one direction (rightward in the figure), and the tracking error signal P has a positive level. (
iii) indicates a state in which a shift occurs in the other direction, and the tracking error signal P becomes a negative level.

Next, the operation will be explained. In this example, it is natural to start the explanation from the time of recording, but the drawings (Fig. 4 (
b) Because of the use of (C)), it is assumed here that some information has already been recorded on the optical recording medium 9 by the tracking control method described later, and the reproduction will be described first. A light beam with reproduction power is emitted from a light source 1 such as a semiconductor laser, the light beam is turned into parallel light by a collimator lens 3, passes through a dichroic mirror 2-6 and a tracking mirror 7, and is sent to an optical recording medium 9 by an objective lens 8. The light is focused onto the recording track 19 as a beam spot 12 as shown in FIG. On the other hand, a light beam for tracking is emitted from the light source 2, and the light beam is transmitted through the collimator lens 4. Half mirror 5, dichroic mirror 6
, passing through the tracking mirror 7.

The objective lens 8 focuses the light onto the optical recording medium 9 as a tracking beam spot 13 at a position a predetermined distance ahead of the reproduction beam spot 12, as shown in FIG.

A part of the beam spot 12 and top king beam spot 13 focused on the optical recording medium 9
The reflected light passes through the objective lens 8, the tracking mirror 7, and the dichroic mirror 6, has its optical path bent by the half mirror 5, and enters the photodetector 11 through the condenser lens 10. The photodetector 11 includes a light receiving section 11a that receives reflected light from the beam spot 12, and the reflected light from the beam spot 12 for reproduction is extracted as a reproduced signal by the light receiving section 11a. Further, the reflected light from the top king beam spot 13 is received by the light receiving section 11b, and the relative positional relationship between the tracking beam spot image 13' and the information track image 19' at that time is shown in FIG. 5(1). As shown in FIG. 5, when the spot center of the tracking beam spot image 13' matches the center (circumferential direction) K of the recording track image 19', the tracking error signal P is zero;
As shown in 1), if the spot center of the tracking beam spot image 13' is shifted in one direction in the radial direction of the optical recording medium 9 (to the right in the figure) with respect to the center of the information track image 19, it is correct. The tracking error signal P of
As shown in Figure Oi+), when the beam spot center of the tracking beam spot image 13' is shifted in the opposite direction (to the left in the figure) with respect to the center of the information track image 19', a negative tracking error signal P is generated. , is output from a circuit not shown. The tracking error signal P at this time is shown in Figure 4 (
As shown in b), the signal waveform has periodic peak values.

Further, the total amount of reflected light from the tracking beam spot 13 is detected in the light receiving section 11b.
A reflected light total amount signal 0 is output from 1b. At this time, the reflected light total amount signal O has a signal waveform that periodically has a peak value at a level lower than a predetermined value E (described later), as shown in FIG. 4 (C1).

Since the reflected light total amount signal O is at a level lower than the predetermined value E, the output of the comparator 14 becomes a low level signal, and the contact a side of the switch circuit 16 remains closed. Therefore, the tracking error signal P is input to the drive circuit 17 through the switch circuit 16, and is transmitted through the tracking coil 18 so that the tracking error signal P is always zero (the beam spot 12 is located directly above the information track 19). The tracking mirror 7 is driven, that is, tracking control during reproduction is performed.

Next, I will explain about recording. A light beam is emitted from the light source 1 at a recording power, and a light beam for tracking is emitted from the light source 2, and each beam passes through the same optical path as during reproduction onto the optical recording medium 9 (Fig. 4 (a)). Focus light. During recording, information is recorded at beam spot 12 (recording pitch)
20) Also, the tracking beam spot 13
A tracking error signal P and a total amount of reflected light signal 0 are obtained by the same operation as during reproduction. The tracking beam spot 13 during recording is shown in Figure 4 (al.
As shown in FIG. 2, the information track 19 is formed so as to be in contact with the innermost track (or outermost track) of the already recorded information track 19.

Note that the spot center of the tracking beam spot 13 at this time is defined as point A. Also, the spot width of the tracking beam spot 13 is (2 x track pitch) -
(information track width).

As a tracking error signal P during recording.

If the tracking beam spot 13 deviates from point A toward the information track 19.

The reflected light from the information track 19 and the reflected light from the unrecorded area enter the light receiving section 11b of the photodetector 11, a positive tracking error signal P is obtained, and the unrecorded area (Fig. 1a) When a shift occurs to the right side, the tracking error signal P becomes zero (Fig. 4 (b1 person')).

Further, when the tracking beam spot 13 is located at point A (the state shown in FIG. 4(a)), the total amount of reflected light signal 0 becomes a voltage E (in this embodiment, the voltage E is a predetermined value). , when a shift occurs toward the unrecorded area, it becomes approximately constant at a level slightly higher than the predetermined value E (FIG. 4(C)). In this embodiment, as can be seen from FIG. 4(C), for example, if the amount of light reflected from the unrecorded portion of information that enters the photodetector 11 is greater than the amount of light reflected from the recorded portion of information, do.

Now, the tracking beam spot 13 is in the unrecorded area (
If a shift occurs in the right direction (FIG. 4(a)), the total amount of reflected light signal O will be at a level slightly higher than the predetermined value E, and a high level signal will be output from the comparator 14 to the switch circuit 16.
The switch circuit 16 is switched from the contact a side to the contact side. Then, a constant voltage is applied from the constant voltage circuit 15 to the drive circuit 17, and the tracking coil 18
Through the tracking mirror 7.

The tracking beam spot 13 is located on the innermost track (
The information track 19) is forcibly driven to move in the direction shown in FIG. 4 (all arrows).

Conversely, if the tracking beam spot 13 deviates toward the information track 19, the 1 reflected light total amount signal 0 becomes a level lower than the predetermined value E, and the switch circuit
16 returns from the contact side to the contact a side, and the positive tracking error signal P obtained at this time is applied to the drive circuit 17 through the switch circuit 16, and the tracking coil 18
The tracking mirror 7 is driven until the tracking beam spot 13 reaches point A (state shown in FIG. 4 (al)).

Through this operation, the tracking beam spot 1
3 moves relatively in the direction of the arrow l' (indicated by the arrow in FIG. 4(a)) while being controlled so as to always be in close contact with the innermost track (information track 19).

Therefore, information is always recorded (by the beam spot 12) at constant or two minute intervals (track pitch).

According to this embodiment, the tracking beam spot 13
Since it is only necessary to place the beam spot 12 in advance of the beam spot 12 and to increase the spot width, it is extremely easy to adjust the position of the optical system and the photodetector, resulting in low cost.

Tracking beam spot 13 with large spot width
By preceding this, it is possible to confirm whether or not the area where information is to be recorded is an unrecorded area. Double recording or overlapping of information tracks can be prevented by configuring a structure in which recording is not performed when a signal exceeding a certain threshold level is detected. In addition, by irradiating the surface of the optical recording medium with a tracking beam spot having a large spot width in advance, the portion to be recorded is bias-heated, and the recording sensitivity can be improved.

In this embodiment, the center of the beam spot 12 and the center of the tracking beam spot 13 are arranged on the same scanning line, but they may be slightly shifted. Also,
Although the tracking beam spot 13 is controlled to be in contact with the nearest information track 19, the spot width of the tracking beam spot 13 becomes thick.
The tracking beam spot 13 may be controlled so that a portion thereof overlaps the nearest information track 19.

As explained above, according to the present invention, a tracking beam spot is formed at a position ahead of the recording beam spot by a predetermined distance in the recording direction, and the width of the tracking beam spot is varied from twice the fixed interval to By setting the information track width to be greater than or equal to the reduced value, the area where the recording beam spot is scheduled to be irradiated and the area at the distance from the information track is pre-scanned by the tracking beam spot. on an optical recording medium that does not have a king track.

The recording beam spot can be guided at a substantially constant track pitch, and the tracking beam spot can be easily formed. Further, by performing advance scanning with a tracking spot having a large spot width, it is possible to confirm whether or not the area where information is to be recorded is an unrecorded area. Furthermore, since the portion recorded by the tracking spot is bias-heated, the recording sensitivity can be improved.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an optical information recording/reproducing apparatus for implementing an embodiment of the present invention, and FIG. 2 is a diagram showing the positional relationship between a recording/reproducing beam spot and a tracking beam spot in an embodiment of the present invention. FIG. 3 is a block diagram showing a part of the tracking control circuit related to this embodiment, and FIG. 4(a) is a diagram showing the positional relationship between the information track and each beam spot. Figure (b) is a diagram showing a tracking error signal corresponding to a change in the radial position of the tracking beam spot 1-13 on the optical recording medium 9, and Figure 4 (C1 is the total amount of reflected light from the tracking beam spot 13). Fig. 5 is a schematic diagram showing the relationship between the light receiving section, the tracking beam spot image, and the information track image 1.2...Light source,
7...Tracking mirror, 9...Optical recording medium,
11--Photodetector, 12--Beam spot, 13-
) Beam spot for racking, 14-・Comparator, 15
... Constant voltage circuit. 16... Switch circuit, 17-... Drive circuit, 19.
−・Information track, P−) Racking error signal, 0・−
Total amount of reflected light signal. Patent Applicant Minoru Nakamura Canon Co., Ltd. Agent Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 (υ (iD (ui)

Claims (1)

[Claims] 1. When controlling the position of a recording beam spot on an optical recording medium that does not have a tracking track so as to maintain a substantially constant interval from an information track that has already been recorded, [the recording beam spot a tracking beam spot is formed at a position a predetermined distance ahead in the recording direction from 5. A tracking control method in which the relative position of the information track to the information track is controlled to be constant.