JPH03222130A - Optical master disk exposing device - Google Patents

Abstract

PURPOSE:To extremely increase the control range of the sectional form of a bit, and to stabilize exposure quality by generating the bit by irradiating the surface of an optical information recording medium by an incident beam transmitted through a dot matrix type optical element. CONSTITUTION:A liquid crystal plate 8 as the dot matrix type optical element is arranged just before an objective lens 5 on an optical path along which laser light emitted from an ion gas laser 1 advances toward an optical master disk 6. This plate 8 is of two-dimensional matrix structure (X,Y axes) provided with a diaphragm function and a shutter function, and the laser intensity distribu tion of the incident beam and the form the bit can be freely controlled by the plate 8. Namely, since even the distribution of the quantity of light of the incident beam can be controlled, and various kinds of exposure patterns can be generated by the control result, the control range of the sectional form of the bit can be increased extremely compared with a traditional device.

Description

[Detailed description of the invention] Industrial applications The present invention relates to an optical disc master exposure apparatus.

2. Description of the Related Art An example of a conventional optical disk master exposure apparatus is shown in FIG. That is, an ion gas laser 1 as a gas laser (in addition, for example,
After passing through multiple mirrors 2, 3 and a lens 4, the laser light emitted from an argon gas laser, etc. enters the objective lens 5 in the form of parallel light, where it is condensed and used as an optical information recording medium. Optical disc master (glass master) 6
irradiated onto the surface of FIG. 8(a) shows an example of the light intensity distribution of the incident beam irradiated onto the optical disc master 6, which allows the formation of pits 7 having the shape shown in FIG. 8(b). I can do it.

Problems to be Solved by the Invention In the conventional optical disk master exposure apparatus as described above, the cross-sectional shape of the pits 7 formed on the surface of the optical disk master 6 is generally controlled by controlling the incident beam. In other words, many approaches to controlling the incident beam focus on adjusting the optical axis of the incident beam and increasing/decreasing the light intensity distribution. Some focus on shape.

However, in this case, there may be a loss of light intensity in the incident beam due to phenomena such as ``vignetting'', and it is also impossible to control the light intensity distribution of the incident beam with this control method. Therefore, there is a problem that it is not possible to stabilize the exposure quality.

Means for Solving the Problems Therefore, in order to solve such problems, the present invention focuses laser light emitted from a gas laser using an objective lens to form a minute spot. In an optical disk master exposure device that creates bits or grooves in a predetermined shape by irradiating laser light onto an optical information recording medium, the laser light emitted from the gas laser is incident on the optical path just before it enters the objective lens. A dot matrix type optical element was installed to control the laser intensity distribution of the beam.

Effect: By passing an incident beam through a dot matrix optical element and then irradiating it onto the surface of an optical information recording medium to form pits, the range of control over the cross-sectional shape of the pits is dramatically increased compared to conventional methods. Furthermore, exposure quality can be stabilized by changing the aperture and transmittance by feeding back the signal of the incident beam.

Embodiment An embodiment of the present invention will be explained based on FIGS. 1 to 6. The overall configuration of the optical disk master exposure apparatus (see FIG. 7) has been described in the prior art section, so a description of the same parts will be omitted, and the same parts will be denoted by the same reference numerals.

A liquid crystal plate 8 as a dot matrix type optical element is disposed on the optical path of the laser beam emitted from the ion gas laser 1, which is located immediately in front of the objective lens 5 while the laser beam is directed toward the optical disc master 6. This liquid crystal plate 8 is
As shown in Figure 2, it has a two-dimensional matrix structure (X, Y axes) with an aperture function and a shutter function, which allows the laser intensity distribution of the incident beam and the shape of the bit 7 to be freely controlled. be able to.

Figure 3 shows the relationship between the voltage applied to the liquid crystal plate 8 and the transmittance, and it can be seen that the transmittance α changes continuously in the range of O to 1.0 depending on the magnitude of the voltage. . In this case, for example, (Xi,,Yi), that is, X
By setting both the xi-th axis in the axial direction and the Yi-th axis in the Y-axis direction, the Lie cell (hatching area) 9 can be made transparent to transmit light, and by turning both the xi-th axis and the Yi-th axis in the OFF state. This makes it possible to make that one cell 9 opaque and block light.

FIG. 4 shows the cross-sectional shape of the liquid crystal plate 8. In the structure in which the twisted nematic liquid crystal 10 is sandwiched between the glass substrates 11, a potential difference is applied between the substrates (on/off). When the liquid crystal plate 10 is turned off), the optical axis within the crystal is rearranged, and by arranging the polarizing plate 12 in front and behind the liquid crystal plate 10, the light transmission state can be changed.

When the liquid crystal plate 8 with the two-dimensional matrix structure is voltage-controlled for all cells in this way, as shown in FIG.
The aperture A and the blocking part B can be created in any shape, and thereby the aperture shape of any aperture can be set. By arbitrarily changing the aperture of the liquid crystal plate 8 having such a structure, the shape of the light intensity distribution of the incident beam passing through the liquid crystal plate 8 can be changed to the sixth shape.
As shown in (a), (c), and (e) in the figure,
It can be changed freely. As a result, a rectangular groove 13 as shown in (b) corresponds to (a), a special groove 14 as shown in (d) corresponds to (c), and (f) corresponds to (e). ) It is possible to create stepped grooves 5 as shown in FIG.

As mentioned above, by providing the liquid crystal plate 8 with a two-dimensional matrix structure, it becomes possible to control even the light intensity distribution of the incident beam, and this makes it possible to create various exposure patterns. It becomes possible to dramatically increase the control range of the cross-sectional shape of the comparison pit 7.

Effects of the Invention In the present invention, the incident beam is passed through a dot matrix type optical element and then irradiated onto the surface of the optical information recording medium to form pits, so the control range of the cross-sectional shape of the pits is greater than in the past. In addition, the exposure quality can be stabilized by changing the aperture and transmittance by feeding back the signal of the incident beam.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a plan view of the dot matrix type optical element, Fig. 3 is a waveform diagram showing the relationship between transmittance and applied voltage, and Fig. 4 is a diagram showing the relationship between transmittance and applied voltage. A cross-sectional view of the dot matrix type optical element, Figure 5 is a plan view of the dot matrix type optical element when the aperture is set to a predetermined state, and Figure 6 shows the light intensity distribution of various incident beams and the pits corresponding to the distribution. FIG. 7 is a configuration diagram showing a conventional example, and FIG. 8 is an explanatory diagram showing a conventional light amount distribution of an incident beam and a pit shape corresponding to the distribution. 1. Gas laser, ・Objective lens, Optical information recording medium, , Pit, Dot matrix type optical element Applicant Rico Co., Ltd. 15 Figure 6 Items (a) (b) A)

Claims (1)

[Claims] Laser light emitted from a gas laser is focused by an objective lens to form a minute spot, and the focused laser light is irradiated onto an optical information recording medium to create pits or grooves in a predetermined shape. The optical disk master exposure apparatus is characterized in that a dot matrix type optical element for controlling the laser intensity distribution of the incident beam is disposed on the optical path immediately before the laser beam emitted from the gas laser enters the objective lens. Optical disk master exposure equipment.