JPS6035340A - Optical recording device - Google Patents

Abstract

PURPOSE:To perform high-reliability recording regardless of the kind of a recording disk by detecting a target value for focusing from a light beam for recording reflected by the recording medium in an information recording device which uses a light beam for automatic focusing separately from the beam for recording. CONSTITUTION:The reflected light of the light beam 20A for recording from the disk 12 is guided to photodetector 15' by a half-mirror 8 through a polarizing prism 18 and a pinhole 7'. This pinhole 7' is formed in a vibrator 19 and oscillates finely in the optical-axis direction. When the vibrator 19 is driven by the output 32A of an oscillator 32 to oscillate the pinhole 7' finely, the output 15A' of the photodetector 15 is as shown in a figure. The output 15A' is detected synchronously by a synchronous detecting circuit 31 with the signal 32A to obtain a high-sensitivity out-of-focus signal whose lead-in range is about + or -5mum. The output 31A of this synchronous detecting circuit 31 is supplied to an automatic focus servo circuit 30 to correct an error in automatic focusing by the output 14A of a photodetector 14.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a device for recording a predetermined information signal using a light beam, and in particular to a device for recording a predetermined information signal using a light beam for recording. The present invention relates to an optical recording device that records information while performing the operation.

[Background of the invention]

For example, in a device that uses a light beam to record a predetermined information signal, such as an optical video disc, the light beam is usually
Since recording is performed by narrowing down the optical spot to a light spot of about μmφ, automatic focusing is an important technique. Conventionally, in many recording apparatuses, a floating head using air pressure is used as an automatic focusing device, and a device consisting of a pinhole and a photodetector is used as a focal position detecting device. This method enables precise focusing for recording, but because a considerable amount of air pressure is applied to the recording surface, it can only be used for substrates that are only slightly deformed by air pressure, such as glass substrates. Further, it has a drawback that the focal position detection range is very narrow, about 5 μm to 10 μm. On the other hand, in playback devices for optical video disks and the like, a voice coil equipped with a stop-down objective lens is usually used as an automatic M4 alignment device. This lifting device and other devices that obliquely irradiate a recording surface with a light beam and detect changes in the position of the reflected light using a position sensor are known. These focal position detection devices have a fairly wide focal position detection range of 100 to 200 μm, but unlike the aforementioned focal position detection devices using pinholes and photodetectors, they do not detect the focal position itself. It has a drawback. That is, by adjusting the positions of the cylindrical lens, position sensor, etc., it is possible to focus the optical spoilers 1 to 2 on the disk surface, or it is also possible to focus them far away from the disk surface. In other words, the autofocus device conventionally used for playback is
It merely has the function of focusing the optical spoiler 1- at a certain distance from the disk surface. For this reason, the positions of the cylindrical lens and position sensor are usually adjusted to maximize the reproduction light output. As described above, the automatic focusing device conventionally used in optical video disc playback devices is effective when the target value for focusing can be clearly detected, and it is difficult to use it as is in a recording device.

Further, Japanese Patent Application Laid-open No. 136051/1983 proposes an information recording apparatus that records with a recording light beam while performing automatic focusing using an optical bismuth having a wavelength different from that of the recording light beam. However, since this device does not detect the target value for focusing, it is unable to perform accurate, stable and reliable recording, and it also has the drawback of increasing the time required for focusing adjustment.

[Purpose of the invention]

It is an object of the present invention to provide an information recording apparatus that can eliminate the above two drawbacks and perform accurate, stable, and highly reliable recording regardless of the type of recording substrate.

[Summary of the invention]

In order to achieve this object, the present invention uses an autofocusing light beam different from the recording light beam to record information by irradiating the recording medium with the recording light beam while performing automatic focusing in b). An information recording apparatus according to the present invention is characterized in that it comprises means for detecting a target value for focusing from a recording light beam reflected by a recording medium.

[Embodiments of the invention]

The present invention will be explained below with reference to Examples.

FIG. 1 is a diagram showing a recording apparatus for explaining one embodiment of the present invention. A laser beam 20 emitted from a recording laser 1 is split by a beam splitter 2 into a light beam 20A for information recording and a light beam 20B for automatic focusing.

Recording laser No. 1 is, for example, an Ar+ laser, and the laser beam 20 is on the straight side. The light beam 20A passes through the optical modulator 3 and is ON-OFF modulated according to the signal 40A from the information source 40. This light beam passes through a half mirror 4, a polarizing prism 5, an auxiliary lens 6, a pinhole 7, and a half mirror 8, passes through a folding mirror 9, passes through a focusing lens 11 attached to a voice coil 10, and passes through a disk. 12 surfaces of the recording medium. The reflected light from the disk 12 is passed through the focusing lens 11.
, mirror 9, mirror 8, pinhole 7,
The light passes through the auxiliary lens 6 and the half mirror 5 and is guided to the photodetector 15 from the half mirror 4. The output of the photodetector 15 when the diameter of the pinhole 7 is 40 μm is shown in FIG.

The horizontal axis represents the amount of deviation of the focal position of the light spot on the disk surface, and the vertical axis represents the output of the photodetector 15. On the other hand, the autofocusing light beam 20B is reflected by the folding mirrors 16 and j7, and is brought into alignment with the recording light beam 2OA by the half mirror 5 at a distance of 3 m from the λ/2 plate 21. The λ/2 plate 21 makes the polarization direction force i f different from the recording light beam by 90', so that the two coincident light beams can be distinguished. The light beam for automatic one point is further guided to the disk surface along the same path as the recording light beam, and its reflected light [Yono1
- The polarizing plate 22 and the cylindrical lens l are
3 and is guided to a 4-split photodetector 14. Polarizing plate 22
was pushed in to allow only the autofocus light beam to pass through. The output 14A of the 4-split photodetector is supplied to an autofocus servo circuit 30, which generates a voice coil drive signal 30A to drive the voice coil 10 to which the diaphragm lens 11 is attached to perform autofocus. This automatic focusing using an automatic focusing light beam and a voice coil is well known.

As mentioned above, a target focal position is required to adjust the position of the cylindrical lens of this automatic focusing device, and in this embodiment, the output 15A of the photodetector 15 is used. That is, as shown in Fig. 2, the output 15A is maximum when the recording light beam is focused on the disk surface, so the position of the cylindrical lens should be adjusted so that the output 15A is maximum. Bye. Also, even if adjusted like this,
A slight deviation of the optical axis of the autofocus light beam, a fluctuation in the power supply voltage of the autofocus servo circuit 30, etc. may cause an error in the voice coil drive signal 3OA, and normal recording may not be performed. In order to prevent this, the output 15A of the photodetector 15 should be monitored immediately before recording.
The offset voltage of the autofocus servo circuit 30 may be finely adjusted so that A is maximized. Figure 3 shows part of the autofocus servo circuit, where a, b, c, and d are the outputs from each of the four-split photodetectors, and 100, 100', and 200 are differential amplifiers. . The output e passes through a subsequent gain adjustment circuit, a phase compensation circuit, etc., and becomes a voice coil drive signal 3OA. In this embodiment, the differential amplifier 200 is provided with offset circuits 1 to 50, so that the fine adjustment described above can be performed by adjusting the variable resistor 50'.

According to the embodiments described above, automatic focusing is performed so that the recording light beam is always focused on the disk surface, and recording can be performed reliably, but since the adjustment is performed manually, recording cannot be performed. It is a pain to have to make fine adjustments every time.

FIG. 4 is a diagram showing a recording apparatus for explaining another embodiment of the present invention. This embodiment automates the fine adjustment described above. In FIG. 4, the reflected light from the disk 12 of the recording light beam 2OA is reflected by a half mirror.
8, the light passes through a polarizing prism 18 and a pinhole 7' and is guided to a photodetector 15'. Here, the polarizing prism 18
In this case, the reflected light of the autofocus light beam 20B is detected by the photodetector 15.
This is to prevent it from entering '. Further, the pinhole 7' is placed at a position optically equivalent to the pinhole 7 in FIG. There are several pinholes 7' in the vibrator 19,
It is designed to allow minute vibrations in the optical axis direction. Vibrator 1
9 is, for example, an electrostrictive element or a voice coil. When the pinhole 7' is stationary, the output of the photodetector 15' is 1.
5A' naturally becomes as shown in FIG. Oscillator 32
Drive the vibrator 19 with the output 32A from the pinball 7
When ' is slightly vibrated, the output of photodetector 15' is 15A'.
is as shown in FIG. If the output 15A' is synchronously detected by the synchronous detection circuit 31 using the signal 32A,
As shown in FIG. 6, a defocus signal with extremely high sensitivity can be obtained with a pull-in range of approximately ±5 μm. The output 3LA of this synchronous detection circuit 31 is connected to the automatic hot spot servo circuit 3.
0, it is possible to correct errors in automatic focusing caused by the output 14A of the photodetector 14. A specific circuit diagram is shown in FIG. This is the circuit part shown in FIG. 3, and instead of the manual adjustment circuit 50, the signal 31A is input to the differential amplifier RJJ amplifier 200, and the signal 1 from the 4-split photodetector 14 is
4A (a, b in Figure 7.

tL is added to the servo signal from each input (C and d).

〔Effect of the invention〕

As described above, according to the present invention, stable recording can be performed even on a plastic disc for which an air-floating lens type recording device cannot be used.

In the above embodiments, the autofocus light beam was created by separating it from the recording laser light, but other laser light such as a He-Ne laser or a semiconductor laser may also be used.

It is also possible to use the reflected light of the recording light beam from the disk as the autofocus light beam, without using the autofocus light beam.

[Brief explanation of the drawing]

1 and 4 are diagrams showing the configuration of a recording apparatus for explaining the present invention, FIGS. 2, 5, and 6 are diagrams showing detection signals of out-of-focus h-views due to pinholes, FIG. 3 and FIG. 7 are diagrams showing the configuration of a part of the autofocus servo circuit. Diagram 5. Figure 1 Figure 7

Claims (1)

[Claims] 1. A first light beam and a second light beam are irradiated onto a recording medium, the first light beam is used to perform focusing, and the second light beam is focused. The apparatus for recording a signal by modulating the signal according to the signal to be recorded includes a light receiving means for receiving the second light beam reflected by the recording medium, and an output of the light receiving means having a vibration component of a predetermined period. and means for extracting the vibration component from the output of the light receiving means, and the focusing is performed so that the output of the means becomes zero. optical recording device. 2. The device according to claim 1, wherein the means for vibrating the second light beam is configured to vibrate the second light beam.
An optical recording device comprising: a pinhole disposed in the optical path of the second light beam; and a vibrating means for vibrating the pinhole along the optical axis of the reflected second light beam.