JPS5994251A - Information recorder - Google Patents

Abstract

PURPOSE:To ensure stable recording by making use of the reflected beam given from a focusing laser beam disk to control the recording laser beam so that it has the light quantity suited to the thickness of a photosensitive film. CONSTITUTION:The focusing laser beam radiated from a focusing laser 27 by an He-Ne laser is reflected on the surface of a disk 26, and this reflected beam is made incident to a focus signal signal detecting 2-split detector 31. The output of the detector 31 is converted into a difference signal of the 2-split output by a comparator 32. This difference signal is applied to a focus controller 33 as a focus control signal, and the sum signal of the output of the detector 31 is obtained by a detecting circuit 34 with the output of the detector 31. This sum signal is supplied to a light quantity controller 35, and the controller 35 calculates the light quantity of the optimum recording beam in response to the thickness of the part of the exposed photosensitive film on the disk 26. Then the result of calculation is applied to an optical modulator 22. The modulator 22 receives the output of the controller 35 and controls the light quantity to be given to the recording laser beam.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates sometimes to devices for recording information using optical means.

[Technical background of the invention and its problems]

Techniques for recording information on a disc using optical means and reproducing information from the disc are well known, for example, in digital audio discs (hereinafter referred to as DAD) and 1) AD players.

After applying a photosensitive agent to the surface of a highly polished glass plate to form a photoresist film, the photoresist film is exposed to a pit shape with a laser beam according to the information. Manufactured from scratch.

FIG. 1 shows an apparatus for recording information on a disk by performing the exposure according to the information to be recorded.

That is, the recording light beam emitted from the recording laser 1 is modulated by the optical modulator Ql), reflected by the mirror 02, and then enters the focusing lens α. The light beam incident on the focusing lens Q3i is focused onto the recording disk I and exposes the photoresist film.

On the other hand, the focusing light beam emitted from the 7 orcus laser α
After passing through the /4 plate (I7) and being reflected by the mirror α barrel, it passes through the focusing lens 0 and is reflected by the recording disk Q4). The reflected beam passes through the mirror Q, is reflected by the mirror U barrel, passes through the '/4 plate, is reflected by the beam splitter UL19, and enters the two-split detector 0 for focus signal detection.

The focus signal can be obtained by detecting the difference between the two outputs of the focus signal detection two-split detector (LI), and after passing through the compensation circuit and drive circuit, it is supplied to the 7 focusing units. .

7. The focusing unit (2) vibrates the focusing lens a3 in accordance with the movement of the recording disk (one fathom) to always focus the recording beam onto the recording disk α◆.

As described above, in the AD manufacturing process and information recording device, the photoresist film on the surface of the glass plate, which is the master of the recording disk, must be as thin as 0.1 μm in thickness. However, it is difficult to form a coating film of uniform thickness.

When recording using a disc with uneven photoresist film thickness,
In the thick part of the photoresist film, the exposure width of the pit shape is narrow.
On the other hand, in thin areas of the film, the exposure width is wide, resulting in unstable recording.

[Purpose of the invention]

The present invention improves the above-mentioned drawbacks of the conventional apparatus, and an object of the present invention is to provide an information recording apparatus that can perform stable recording even if the thickness of the photoresist film on the recording disk is uneven.

[Summary of the invention]

In order to achieve the above object, the present invention utilizes the beam reflected from the disk of the focusing laser beam,
To obtain stable recording by detecting a signal related to the thickness of the photoresist film on the disk and controlling the recording laser beam based on the output so that the amount of light is optimal for the thickness of the photoresist film. This is what made it possible.

[Embodiments of the invention]

Hereinafter, one embodiment of the information recording device according to the present invention will be described in detail with reference to FIG. For example, a recording laser beam emitted from a recording laser Cυ is sent to an optical modulator (2) and is modulated according to a digital signal from an information source 12 that is added to this modulator. After the output beam of the modulator Q is reflected by a mirror,
The light enters the focusing lens Q [with]. The beam incident on the focusing lens (c) is focused on the recording disk (c) and
The upper photoresist film is exposed to form pit-shaped exposed portions corresponding to the digital signal.

On the other hand, the focusing laser beam emitted from the focusing laser (5), for example, an H-Ne laser, passes through the beam splitter 2/4 plate, is reflected by the mirror, and then is reflected by the focusing lens ( c) It is focused on the recording disk. The focusing beam irradiated onto the disk (C) is reflected by the surface of the disk (C). This reflected beam passes through a mirror, is reflected by a similar mirror, passes through a 2/4 plate (to), is reflected by a beam splitter (c), and enters a two-split detector OD for focus signal detection. The output line comparator 6 of this detector 0υ converts it into a difference signal between the two divided outputs.

This difference signal is used as a focus control signal to
/1 is added to the rectifier (c). The output of the focus signal detection two-divided detector 01) is used by a detection circuit to obtain a sum signal of the outputs of the two-divided detector r31). This sum signal is input to the light amount control device 0, where the optimum light amount of the recording beam is calculated according to the thickness of the exposed portion of the photoresist film on the disk (c), and the result is used for optical modulation. The light modulator (24) is applied to the light amount control device (24).
Receiving the output of the song controls the light intensity of the recording laser beam.

In the figure, (to) is the turntable, 0η, (to) is the motor, 0I is the CLV (constant linear velocity) rotation servo circuit, Gi
n is the radial feed servo circuit, turntable (
This device rotates the disc-shaped recording medium (c) placed on the disc (g) at a predetermined speed.

Incidentally, there is a relationship between the thickness of the photoresist film and the reflectance of the light beam as shown in the following equation, and the reflectance is expressed as a function of the thickness of the photoresist film.

I = TI + r2 + 2rlrlcos (g-r) where: reflectance nl: refractive index of photoresist film n! refractive index of Nigarasu d: film thickness of photoresist film λ: wavelength of beam Figure 3 is a graph showing the relationship between reflectance and film thickness of photoresist film, nl = 1.6, nfi:= 1.51
, is an example of λ-6328A.

However, this means that the amount of light of the focused reflected beam includes information on the film thickness of the photoresist film, and this film thickness information is represented by the sum signal of the outputs of the focus signal detection two-split detector c31). The light amount control device (c) has an arithmetic function to obtain an output based on film thickness information obtained from the relationship between the reflectance and the photoresist film thickness.

In this way, the light intensity of the recording laser beam becomes a light intensity suitable for the thickness of the photoresist film, and even when the photoresist film is thick, the width of the recorded bit shape may be reduced due to insufficient light intensity of the recording light beam. Stable recording can be performed without causing fcb, where the width of the bit shape becomes wider, or vice versa.

Furthermore, in the embodiments described above, the optical modulator can be omitted by using a semiconductor laser that can directly modulate the amount of light.

〔Effect of the invention〕

According to the present invention, as described above, it is possible to obtain stable recording even with respect to unevenness in the thickness of the photoresist film of a disc-shaped recording medium. The present invention also relates to a capacitive video disc style 2.
It can also be applied to recording grooves as deep as 5 μm, such as with a polishing machine.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a conventional information disk recording device, Fig. 2 is a block diagram showing an embodiment of the present invention, and Fig. 3 is a characteristic curve diagram showing the relationship between reflectance and photoresist film thickness. be. 21... Recording laser 22... Optical modulator 2
3... Information signal source Mu... Mira -25
...Focusing lens 26...Disk-shaped recording medium 2
7...Laser for focus Imperial...Beam slit 29...2/4 plate 30...Mirror -31...2-split detector for focus signal detection 32...Comparator 33...Focus Adjuster 34... Sum signal detection circuit 35...
- Light amount control device 36... turntable 37.
38...Motor 39...CLV rotation servo circuit 40...Radial transmission servo circuit Agent Patent attorney Noriyuki Chika (and 1 other person) Figure 1

Claims (1)

[Claims] A drive device that rotates a disk-shaped recording medium coated with a photoresist film on its surface at a predetermined speed, a beam generator that generates a recording laser beam modulated by a recording information signal, and this beam generator. a device that irradiates the photoresist film of the medium with the laser beam to expose the photoresist film; a focusing laser beam generator that emits a focusing beam to properly focus the laser beam on the medium; a device for irradiating the medium with a laser beam from the focusing laser beam generator;
a focus signal detection device that detects the amount of the focusing beam reflected by the medium; a device that uses the amount of the reflected beam of the focusing beam as an input to obtain an output related to the thickness of the photoresist film of the medium; An information recording device comprising: a device for controlling the amount of recording laser beam light directed to the photoresist film based on the output of the device.