JPS6344322A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To obtain an exact tracking error signal and to execute stable autotracking by setting a memory region in a narrow range in the longitudinal direction of tracking tracks. CONSTITUTION:Since a recording layer 3 is provided only in the region between boundaries 7a, 7b of an optical card 1, recording of information is not possible at both ends in the longitudinal direction of the card 1. The memory region 6 for forming recording bits 5 is provided between plural pieces of the tracking tracks 4. A side spot S1 has the track 4a to follow up even if a main spot S2 is projected to the recording bit 5 at the rightmost end; therefore, the balance in the quantity of the return light between the side spots S1 and S3 is maintained. Since the exact tracking error is thereby obtd., the stable autotracking is executed.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an optical information recording medium, and in particular to a card-shaped recording medium in which recording pit rows are formed in parallel and straight lines. The present invention relates to an optical information recording medium that is improved so as to be able to perform the following operations.

(Prior Art) Conventionally, various types of media such as disk-shaped, cart-shaped, and tape-shaped media are known for optically recording information and reproducing the recorded information. Among these, card-shaped optical information recording media (hereinafter referred to as optical carts) are expected to be in great demand as small, lightweight, highly portable media with a large storage capacity.

As shown in FIG. 4, such an optical card has a rectangular base 21 made of a flexible plastic sheet or the like.
The recording layer 22 is provided with a recording layer 22 capable of forming a clear record pit array that can be recorded and reproduced by a light beam irradiated from an objective lens, as will be described later.

In order to record information on such an optical cart, a light beam modulated according to an information signal and focused by an objective lens is irradiated onto the surface of the recording layer 22. (Hereinafter, the recording focus row formed as described above is referred to as a track.) Also, for the optical cart on which the recording bits are formed as described above, To reproduce information using an optical head, a light beam is emitted from an optical head onto a track, and a photodetector is used to detect differences in the amount of light reflected back to an objective lens provided in the optical head depending on the presence or absence of recording pits. Detect and reproduce as an electrical signal.

By the way, in order to perform recording and reproduction on this type of optical card, the optical card is moved in a straight line relative to the optical head so that the light beam emitted from the optical head follows the track of the optical card. Therefore, auto-tracking (hereinafter referred to as AT) is used to prevent the light beam from deviating from the desired track when the optical card oscillates or there is an error in the optical cart mounting section. .

(Problems to be Solved by the Invention) The 3-beam system is a well-known method for performing this AT. In this method, the main beam is incident on a transmission type diffraction grating, and is split into a total of three beams: the main beam that passes through the grating as it is, and the ±1st-order diffracted light, that is, a pair of sub-beams. As shown in (b), the sub-beam is irradiated with a slight deviation from the center of the track 13 to form a main spot 16 and a pair of sub-spots 15°17.

In this case, the main spot 16 scans the center of the track 13 in the B direction and forms recording pits 14 (shaded area in the figure) according to the information signal as shown in the figure, or as shown in FIG. The bit string (track 13) formed as shown in b) is scanned to reproduce information.

On the other hand, the sub-spots 15.17 are used for tracking error detection, and when tracking is performed accurately, each spot 15.17 is in a state where half of it lies on the boundary of the track 13, as shown in the figure. Become. In this state, the amount of light that is reflected once and returns to the objective lens is
Both 5 and 17 are equally balanced.

On the other hand, if the sub-spot 15.17 shifts to the left, for example in the direction of arrow B, then the left sub-spot 17
When the sub-spot 15 on the right side deviates from the track 13 and shifts to the right in the direction of arrow B, the right sub-spot 15 deviates from the track 13, and the amount of return light of each of the sub-spots 15 and 17 changes.

Thus, by taking the difference between the photodetectors for the pair of sub-spots 15 and 17, a tracking error signal can be obtained.

However, in such a conventional AT, as shown in FIG.
As is clear from a) and (b), the sub-spot 15.1 used for detecting the tracking error signal
Since there are recording pits 14 within the scanning trajectory of No. 7, that is, on the track 13, there is a problem in that the signal detected from the recording pit 14 is mixed into the tracking error signal, making it impossible to perform stable AT. Ta.

Particularly, as shown in FIG. 5(a), when recording information, since the recording pit 14 exists only on the side of the sub spot 15 that is additionally struck on the main spot, both sub spots 15.
A significant imbalance occurred in the tracking error signal from No. 17, resulting in a problem that an accurate tracking error signal could not be obtained.

Therefore, the present invention has been made to solve the above problems, and it is possible to obtain an accurate tracking error signal without mixing the signal detected from the recording pit with the track into the tracking error signal, and to perform stable AT. The purpose of this invention is to provide an optical information recording medium that can

(Means for Solving the Problem) The problem with the prior art described above is that the tracking tracks of the present invention are arranged at regular intervals, and information is recorded by irradiation with a light beam provided between the tracking tracks. This problem can be solved by an optical information recording medium having a recording area, the recording area being set in a narrow range in the longitudinal direction of the tracking track.

(Function) In the optical information recording medium of the present invention configured as described above, the tracking track provided for obtaining a tracking error signal separates the recording area in which the recording pit row is to be formed and its trajectory. Therefore, when obtaining a tracking error signal by irradiating the tracking track of such a recording medium with the sub-beams of both sites among the three divided light beams, the sub-beam that additionally hits the central main beam is formed by the main beam. Since the sub-beams are not irradiated with recorded bits, information signals from the recorded bits are not mixed into the sub-beams, and thus both sub-beams can detect tracking error signals under equal conditions.

Furthermore, in the present invention, since the tracking track has an area in which no recording area is set at the longitudinal end, no recording bits are formed in the area, and the recording bit string is located at the longitudinal end of the recording bit string. Is it the main spot for the recording bit? ! ! Even when the two sub-beams are emitted, the preceding sub-beam does not deviate from the tracking track, and the tracking error signal can be detected under equal conditions for the two sub-beams as described above.

(Example) An example of the present invention will be described below with reference to the accompanying drawings.

Note that an optical cart will be used as the optical information recording medium in the embodiments described below.

Among the accompanying drawings, FIG. 1 is a schematic plan view of the optical card of this embodiment, and FIG. 2(a) is an enlarged view of the main part of the recording area of the optical cart, showing the irradiation of the three-divided beam spot. Fig. 2(b) is an enlarged view of the main part showing a modification of Fig. 2(a), and Fig. 3(b) shows the irradiation situation at the end of the optical card shown in Fig. 1. It is an enlarged view of the main part shown.

In FIG. 1, an optical card 1 comprises a flexible rectangular substrate 2 such as a plastic sheet, and a recording layer 3 formed of a silver salt-based, dye-based, or Calcoken rod. It is something. The recording layer 3 is provided only in the areas shown by 73 and 7b in the figure, and therefore information cannot be recorded at both ends of the optical cart 1 in the long side direction. There is.

A plurality of strip-shaped tracking tracks 4 are provided in parallel to each other in a straight line along the long side direction of the optical card l. Such a tracking track is created, for example, by forming several #i grooves on the substrate.

Therefore, at the M end in the long side direction of the optical card l, only a plurality of tracking tracks 4 are provided on the base body 2 with boundaries 7a and 7b as the boundaries. And between 7a and 7b, there are multiple 1
~Racking track 4 and in between, as will be explained later,
It has a plurality of recording areas 6 in which recording bits 5 are to be formed.

In order to record information on the optical cart L configured as described above or to reproduce recorded information, a first sight spot Sl and a main spot S2, which are divided into three parts by a transmission type diffraction grating (not shown), are used. A second side spot S3 is irradiated. Among these spots, the main spot S2 is used for detecting an autofocusing error signal, forming recording bit 5 during recording, or detecting recorded information during playback, and the sight spots S, S are used for detecting an autotracking error signal. used.

Furthermore, since the light intensity distribution of these sight spots S1, Sv on the optical card is usually a Gaussian distribution with a high concentration in the center, each of these sight spots S1, Yt and Sv is divided into half or half of the tracking track 4a.

4b, the change in the return light caused by track deviation becomes large, and it is advantageous to be able to detect a tracking error signal with high sensitivity.

In addition, in FIG. 2(a), the irradiation position of the side spots S, S, is on the near side boundary line of both tracking tracks 4a, 4b adjacent to the recording area 6, or is different from this. , as shown in FIG. 2(b), may be located on the boundary line on the far side from the recording area 6.

Also, beam spots S□, S2. The diameter of S (if these spots are not circular, the radius perpendicular to the track) is D1. D2. Assuming Dy, it is desirable that vAW of the tracking tracks 4a and 4b satisfies W≦D, (=D,) (1). This is because if the spot diameter is larger than the tracking track width, if any of the sight spots falls completely within the tracking track, no change in light intensity will occur in response to the movement of the beam spot in the direction perpendicular to the track. It is.

Furthermore, the interval between tracking tracks, that is, the convergence of the recording area between tracking tracks, is L≧D2+1/
2 D, +1/2 Dyu ("D2+DI)...(2
), this is the main spot S2
This is to prevent the recording pits 5 formed by the side spots SI or S2 from being detected by the side spots SI or S2, thereby obtaining a stable tracking error signal.

Therefore, from equations (1) and (2), the recording medium of this embodiment should be configured such that the spacing between the tracking tracks is at least twice the radius W of the tracking tracks, that is, the relationship L≧2W is satisfied. .

Next, other functions of this embodiment configured as described above will be explained in detail.

As shown in FIG. 3(a), the spacing of the t-tracking tracks and the vAW of the tracking tracks are L as described above.
Even if the configuration satisfies the relationship ≧2W, if the recording pits 5 or the tracking tracks 4a, 4b, 4c are formed to the end of the optical card l in the long side direction, the end of the recording pit 5 or the tracking track 4a, 4b, 4c may Main spot S2 for recording pit 5
In this case, the first site spot SI loses the tracking track to be followed, and the amount of return light from the side spots S1 and 82 becomes unbalanced, making it difficult to perform stable AT. become unable.

However, in this embodiment, in order to deal with such a situation, as shown in FIG. 3(b), at least the diameter of the sight spot S or S2 (these are If the spot is not circular, there is an area (to the right from 7b in Figure 3(b)) where no recording pits are formed at an interval of at least the length of the spot. Even when the recording pit 5 is irradiated with the main spot S2, the first side spot S has a tracking track to follow. Therefore, the amount of return light from the first and second sight spots S1 and S2 can be kept in balance, and stable AT can be performed.

In the embodiments described above, the recording area is limited to the portion where the recording layer is provided, but the recording area may be a portion narrower than the recording layer. In this case, the recording area is limited, for example, by providing an optical detection mark in the recording layer.

Although the present embodiment has been described above using an optical card as the optical information recording medium, the present invention can also be applied to other optical information recording media such as sheet-shaped optical information recording media.

(Effects of the Invention) As explained above, according to the optical information recording medium of the present invention, when detecting a tracking error signal by the 3-beam system, the optical information recording medium used for detecting the tracking error signal
Of the two sub-beams, the sub-beam that additionally strikes the main beam does not scan the recording pits formed by the main beam, so the sub-beam does not contain any information No. Therefore, one sub-beam can detect a very accurate tracking error signal under uniform conditions.

Furthermore, even when recording pits are formed at the extreme ends of the recording area with the main beam or information signals are obtained from the recording pits, the sub-beam preceding the main beam does not deviate from the tracking track to be followed; The sub-beams can always obtain very accurate tracking error signals under uniform conditions.

Thus, according to the optical information recording medium of the present invention, stable AT can be performed.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an optical card according to an embodiment of the present invention, m2
Figure (a) is an enlarged view of the main part of the optical card in Figure 1, showing the irradiation status of the three-divided beam spot, and Figure 2 (b) is an enlarged view of the main part showing a modification of Figure 2. Figure, 3rd
Figure (a) is an enlarged view of the main parts to explain the irradiation situation at the end of the optical cart shown in Figure 1, and Figure 3 (b) shows the irradiation situation at the end of the optical cart shown in Figure 1. An enlarged view of the main parts, Figure 4 is a schematic plan view of a conventional optical card, and Figure 5 (a) is an enlarged view of the main parts of the optical card shown in No. Figure 5(b) shows the situation at the time of recording, and Figure 5(b) shows the situation at the time of playback in Figure 5 (@. ■... Optical cart, 2... Substrate, 3...・Record R layer, 4
... Tracking track, 5 ... Recording pit, 6
...recording area, S2...main spot, S+,
S3 "" Sub spot Figure 1 Figure 2 (a) Pull Figure 2 (b) Figure 3 (0) c Toe 7b Figure 4 Figure 5

Claims (1)

[Claims] (1) Tracking tracks arranged at regular intervals,
and a recording area in which information is recorded by irradiation with a light beam provided between the tracking tracks, and the recording area is set in a narrow range in the longitudinal direction of the tracking track with respect to the tracking track. An optical information recording medium characterized by: