JPS6132233A - Additional recording type optical head - Google Patents

Abstract

PURPOSE:To improve tracking accuracy greatly by splitting a light beam emitted by a single light source into two light beams which are different in the quantity of light and using the beam which is less in the quantity of light as an auxiliary beam for additional recording. CONSTITUTION:Three switches 27-29 are all placed at sides of an adding and subtracting circuit 26 during the additional recording. The light source 11 emits a writing light beam which whose quantity is about 10 times as large as that during reproduction according to the output of a modulating circuit, and a new pit is formed at a specific position on a track 2 with the 1st light beam 21 split by a polarization beam splitter 13. At the same time, the return light of the 2nd light beam split by the polarization beam splitter 13 is incident on a four-split photosensor 20. A focusing error voltage Vfe and a tracking error voltage Vte outputted through switches 27 and 28 are utilized for focusing servo and tracking servo during the additional recording operation respectively.

Description

[Detailed description of the invention] Purpose of invention Industrial applications The present invention relates to an additional recording type optical head.

2. Description of the Related Art Currently, optical storage devices that combine an optical head and an optical disk are attracting attention as small-sized, large-capacity storage devices.

Among these types of optical storage devices, the simplest type is number 1: This is a device exclusively for relocation, and is used as a video disk, digital audio disk (D A D), etc.
It is already becoming popular in ordinary households.

In the future, this type of optical storage device will also become a magnetic storage device and a semi-dedicated storage device.
, a device, it is thought that it will develop into a rewritable device. At present, additional recordable devices that occupy an intermediate position between reproduction-only bag holders and rewritable devices are being commercialized.

The add-on recording device is configured not only to be able to reproduce the information written on the optical disc at the time of manufacture, but also to allow the user to additionally write desired information. Furthermore, information can be erased by forming continuous focus 4). However, since information is written by irradiating a laser beam onto a metal thin film formed on the optical disc and forming a small hole (called a focus) with heat, the written information can be changed. I can't do that.

The problem that the invention seeks to solve.

In the above-mentioned conventional additional recording type device, since the return light during additional recording contains large noise, tracking servo and making servo are performed based on the return light in the same way as during playback, which improves the tracking accuracy. decreases, and in severe cases,
There is a problem with the truck jumping.

In the conventional configuration, in which pits are formed in a metal thin film and servo operation is performed based on the reflected light (return light) from the pits that are being formed, 2. Compared to the reproduction operation in which information is reproduced from the pits that have already been created, It is considered inevitable that the returned light will contain a large amount of noise.

In reproduction-only equipment that reproduces information using the self-coupling effect caused by the return light of a semiconductor laser.

In some cases, a light source separate from the reproduction light source is used to create an auxiliary beam for the servo. It is conceivable to apply this configuration of the auxiliary beam J with a separate light source to an additional recording device, but using two light sources and light guide systems has the problem of increasing manufacturing costs and making adjustments complicated. There is.

Structure of the Invention Means for Solving the Problems The present invention solves the problems of the prior art as described above. a light beam splitting means for splitting the light beam into the first and second light beams; A light guide means for guiding a second light beam to different locations on the track; and performing a servo operation based on the returned light of the second light beam during additional recording.

The apparatus is configured to include a servo system that performs a servo operation based on the returned light of the first light beam during reproduction.

Hereinafter, the operation of the present invention will be explained in detail by way of examples.

Embodiment FIG. 1 is a block diagram showing the configuration of an embodiment of an additional recording type optical head of the present invention together with an optical disk.

In this additional recording type optical head 10, 11 is a single light source, 12 is a collimating lens, 13 is a polarizing beam splitter, 14 is a half mirror, 15 is a reflector, 116 is an objective lens, 17 is a converging lens, 18 is a cylindrical lens, and 19.20 is a light sensor.

Light source 11 is preferably composed of a semiconductor laser.

The light beam J, emitted from the light source 11 is turned into a parallel beam by the collimating lens 12.

The light passes through a prism J, etc. (not shown) for improving the ellipticity of the beam cross-sectional shape, and then enters the polarizing beam splitter 13.

Polarizing beam splitter 13 is preferably.

It consists of a Wollaston prism made of crystal, etc., which opens the incident beam and produces a first light beam 2 at an angle of several degrees.
1 and a second light beam 22.

The light intensity distribution between the first light beam 21 and the second light beam 22 is set by rotating the light source 11 around its optical axis and adjusting the polarization direction of the incident light and the crystal axis of the polarizing beam splitter 13. This is done by changing the angle. The first light beam 21 is 10 to 2 times larger than the second light beam 22.
The light source 11 is rotated so that the amount of light is approximately 0 times greater. The first beam split by polarizing beam splitter 13
゜The second light beams 21 and 22 are formed by three half mirrors 14,
A light guide system consisting of a reflector 15 and an objective lens 16 irradiates light onto different locations on the track 2'' formed on the optical disk 1, separated by approximately several tens of micrometers.

Each of the return lights reflected from the optical disk 1 travels in the direction opposite to the direction in which they entered the light guide system.

A portion reflected by the half mirror 14 is sent to the converging lens 17
incident on . Each return light converged by the converging lens 17 is cylindrical to generate astigmatism.
The light passes through the lens 18 and enters the light sunners 19 and 20, respectively.

The optical sunners 19 and 20 are, as shown in FIG.
It consists of a 4-split optical sunner. The output of each four-split optical scanner is supplied to addition/subtraction circuits 25 and 26, each consisting of an adder and a subtracter.

Each adding/subtracting circuit has exactly the same configuration, and by adding and subtracting the optical voltages supplied from each section of the corresponding 4-split optical scanner, the focusing error voltage Vfe
+I.Outputs racking error voltage Vte and reproduction signal voltage Vrs.

That is, in each 4-split optical scanner, the difference between the light amounts in the two diagonal directions gives a focusing error voltage Vfe based on the cross-sectional shape of the returned light in the astigmatism method, and the deviation of the spot center of the returned light from the section boundary line The amount gives a tracking error voltage Vte, and the sum of the amounts of returned light incident on the 24 sections gives a reproduction signal voltage Vrs indicating the presence or absence of pits on the track.

At the time of additional recording, all three switches 27 to two are switched to the addition/subtraction circuit 26 side, as shown in FIG. The light source 11 emits a writing light beam having a light intensity approximately 10 times greater than the light intensity during reproduction according to the output of a modulation circuit (9) not shown, and is split by a polarizing beam splitter 13 into a first light beam. By 21,
+-A new pit is formed at a predetermined location on the rack 2. At the same time, the return light of the second light beam split by the polarizing beam splitter 13 enters the four-split optical scanner 20.

Focusing error voltage Vfe and tracking error voltage Vte output through switches 27 and 28, respectively.
is used for focusing servo and trunking servo during this additional recording operation. The reproduction signal voltage Vrs outputted through the switch 29 is supplied for purposes such as checking whether the above-mentioned additional recording has been performed or not, and searching for the point at which erasing has started due to the formation of continuous pips. Ru.

During the above additional recording, the other 4-split optical scanner 19
The return light of the first light beam is incident on the , but this return light contains large noise due to the formation of pits.
None of the focusing error voltage Vfe, l-racking error voltage Vte, and reproduction signal voltage Vrs output from the addition/subtraction circuit 25 is used.

During the above additional recording, the 4-split optical scanner 19 has the following information:
The amount of returned light that is 10 times greater than the amount of returned light during reproduction is incident. This is to avoid deterioration or destruction of the 4-split optical scanner 19 and the addition/subtraction circuit 25 due to this large amount of returned light.

A light shielding plate 30 is installed as necessary. This light shielding plate 3
0 may be one that opens and closes in a nuclear manner, such as an analyzer r whose polarization plane can be rotated by an electrical signal.

The light transmittance decreases as the number of light meters increases, such as photochromic light transmitting plates, or the light transmittance decreases depending on the voltage applied during additional recording, such as electronic chromic materials, liquid crystals, etc. The light rate may be reduced.

When performing a playback operation, the three switches 27 to 29 are
Both are switched to the addition/subtraction circuit 25 side in the opposite direction to that shown. From the light source 11, the amount of light at the time of additional recording described above is 10
A reproducing light beam J having a light intensity as small as 1/2 is emitted, and information is read from a predetermined location on the track 2 by the first light beam 21 which is divided into N parts by the polarizing beam splitter 13. It will be done. In other words, the amount of returned light depending on the presence or absence of pits is incident on the four-split light beam 719. The focusing error voltage Vfe and tracking error voltage Vte output through the switches 27 and 28 are used for focusing servo and tracking servo during this reciprocating operation. The reproduction signal voltage Vrs outputted via the switch 29 is used for information reproduction.

-1- During the reversal operation, the other 4-split light beam 7 20
The second beam split by the polarizing beam splitter 13 is shown in FIG.
The return light of the light beam is incident. The amount of this returned light is 1
This is a small value of about 1/10 of the amount of returned light under normal reciprocating operation. Therefore.

The focusing error voltage Vfe, ) ranking error voltage Vte, and reproduction signal voltage Vrs outputted from the addition/subtraction circuit 26 are not used because they all have low S/N ratios. Note that, if necessary, the low level output of the adder/subtractor circuit 26 can be used for calibrating the optical sensor sensitivity or detecting S/N deterioration.

In the above embodiment, the light amount splitting ratio of the polarizing beam splitter 13 was kept constant during additional recording and reproduction.
By rotating the light source 11 during reproduction, it is also possible to further increase the above-mentioned light amount division 1 to increase the light utilization efficiency.

In addition, although the configuration for obtaining the tracking error voltage and the focusing error voltage using the astigmatism method and the 4-split optical system is illustrated, the configuration is not limited to this, and any suitable method for obtaining the above error voltage may be used. good.

The first part is further divided into two parts. Although a configuration has been exemplified in which the second light beam is guided to different locations on the same track, the second light beam may be configured to be guided to different locations on the same track.

In the second invention related to the present application, the half mirror 14. The light guide system consisting of the reflector 15 and the like includes the first. The second light beams 21,22 are arranged to be directed onto respective adjacent tracks.

Under such a configuration, an additional recording operation that is exactly the same as the above-mentioned additional recording operation is performed.

On the other hand, during reproduction, one or both of the light source 11 and the polarizing beam splitter 13 is rotated around its tip axis,
A first light beam 21 and a second light beam 22 having substantially equal amounts of light are emitted from the polarizing beam splitter 13.

The return lights of the respective light beams are incident on the optical sensors 19 and 20, and the reproduction signal voltages Vrs for two adjacent tracks are simultaneously read out from the adder/subtractor circuits 25 and 26 and supplied to the recirculation circuit. At the same time, a servo operation is performed based on the focusing error voltage Vfe and the tracking error voltage Vte output from one or both of the addition/subtraction circuits 25 and 26.

By rotating the light source, etc., the first. Although a configuration has been illustrated in which the light amount ratio between the second light beams is changed, the light amount ratio may be made variable by installing a transparent plate with variable light transmittance in the optical path.

As described above, according to the second aspect of the invention, the additional recording operation is performed for each track, but the reproducing operation is performed for each two tracks, which has the advantage that the reproducing speed can be doubled.

Effects of the Invention - F As explained in detail, the additional recording optical head of the present invention splits the light beam emitted from a single light source into two light beams with different amounts of light, and splits the light beam emitted from a single light source into two beams with different amounts of light. Since it is configured to be used as an auxiliary beam during additional recording, the i8
This has the effect of significantly improving tail accuracy.

Further, the additional recording type optical head of the present invention does not require one light source for generating the auxiliary beam.

It has the advantage of being inexpensive to manufacture and requiring only a department to make adjustments.

Furthermore, since the additional recording type optical system according to the second aspect of the present invention can simultaneously reproduce information for two tracks, it is possible to double the reproduction speed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention together with an optical disk 1, and FIG. 2 is a block diagram showing the configuration of an embodiment of the present invention together with an optical disk 1. FIG.
- Sensors 19 and 20 are not shown with their attached circuits.
-11...Light g, ]2...Collimating lens. 13...Polarizing beam splitter, 14...Half...
Mirror, 15...Reflector-916...Objective lens,
17. Converging lens, 18. Cylindrical lens, 19.20. Optical sunna. 25.26... Addition/subtraction circuit. Patent applicant: NEC Home Electronics Co., Ltd.

Claims (4)

[Claims] (1) In an additional recording optical head capable of playback and additional recording, the light beam emitted from a single light source is
a light beam splitting means for splitting the first and second light beams into a light beam and a second light beam having a small amount of light; and a light guide means for guiding the split first and second light beams to different locations on the same track or onto different tracks. During additional recording, additional recording is performed using the first light beam, and servo operation is performed based on the return light of the second light beam, and during reproduction, information is reproduced and reproduced based on the return light of the first light beam. 1. An additional recording type optical head characterized by comprising means for performing servo operation. (2) The additional recording type optical head according to claim 1, wherein the light beam splitting means is a Wollaston prism. (3) In an additional recording type optical head capable of playback and additional recording, the light beam emitted from a single light source is divided into a first light beam with a large light intensity and a second light beam with a small light intensity during additional recording. a light beam splitting means for splitting the first and second light beams into first and second light beams having substantially equal amounts of light during reproduction; a light guiding means for guiding the split first and second light beams onto different tracks; During additional recording, additional recording is performed using the first light beam, and a servo operation is performed based on the return light of the second light beam, and during playback, different tracks are recorded based on the return light of the first and second light beams. 1. An additional recording type optical head, comprising means for performing a servo operation based on one or both of the respective return beams while simultaneously reproducing the above information. (4) The light beam splitting means is a Wollaston prism, and the light quantity ratio of the first and second light beams is varied by rotation of the light source around the optical axis. The additional recording type optical head described in item 3.